diff --git a/layout/base/nsCSSRendering.cpp b/layout/base/nsCSSRendering.cpp
index 20995170abfa..71b35c2de5af 100644
--- a/layout/base/nsCSSRendering.cpp
+++ b/layout/base/nsCSSRendering.cpp
@@ -667,6 +667,10 @@ nsCSSRendering::PaintBorder(nsPresContext* aPresContext,
   }
 
   nsStyleBorder newStyleBorder(*styleBorder);
+  // We could do something fancy to avoid the TrackImage/UntrackImage
+  // work, but it doesn't seem worth it.  (We need to call TrackImage
+  // since we're not going through nsRuleNode::ComputeBorderData.)
+  newStyleBorder.TrackImage(aPresContext);
 
   NS_FOR_CSS_SIDES(side) {
     nscolor color = aStyleContext->GetVisitedDependentColor(
@@ -678,6 +682,11 @@ nsCSSRendering::PaintBorder(nsPresContext* aPresContext,
                                aDirtyRect, aBorderArea, newStyleBorder,
                                aStyleContext, aFlags, aSkipSides);
 
+  // We could do something fancy to avoid the TrackImage/UntrackImage
+  // work, but it doesn't seem worth it.  (We need to call UntrackImage
+  // since we're not going through nsStyleBorder::Destroy.)
+  newStyleBorder.UntrackImage(aPresContext);
+
   return result;
 }
 
@@ -5023,13 +5032,8 @@ ShouldTreatAsCompleteDueToSyncDecode(const nsStyleImage* aImage,
     return false;
   }
 
-  imgRequestProxy* req = aImage->GetImageData();
-  if (!req) {
-    return false;
-  }
-
   uint32_t status = 0;
-  if (NS_FAILED(req->GetImageStatus(&status))) {
+  if (NS_FAILED(aImage->GetImageData()->GetImageStatus(&status))) {
     return false;
   }
 
@@ -5037,7 +5041,7 @@ ShouldTreatAsCompleteDueToSyncDecode(const nsStyleImage* aImage,
     // The image is "complete" since it's a corrupt image. If we created an
     // imgIContainer at all, return true.
     nsCOMPtr<imgIContainer> image;
-    req->GetImage(getter_AddRefs(image));
+    aImage->GetImageData()->GetImage(getter_AddRefs(image));
     return bool(image);
   }
 
@@ -5074,9 +5078,8 @@ nsImageRenderer::PrepareImage()
   }
 
   switch (mType) {
-    case eStyleImageType_Image: {
-      MOZ_ASSERT(mImage->GetImageData(),
-                 "must have image data, since we checked IsEmpty above");
+    case eStyleImageType_Image:
+    {
       nsCOMPtr<imgIContainer> srcImage;
       DebugOnly<nsresult> rv =
         mImage->GetImageData()->GetImage(getter_AddRefs(srcImage));
diff --git a/layout/base/nsDisplayList.cpp b/layout/base/nsDisplayList.cpp
index 318e592eb180..e04f3352828a 100644
--- a/layout/base/nsDisplayList.cpp
+++ b/layout/base/nsDisplayList.cpp
@@ -2864,9 +2864,7 @@ nsDisplayBackgroundImage::ShouldCreateOwnLayer(nsDisplayListBuilder* aBuilder,
     if (image->GetType() == eStyleImageType_Image) {
       imgIRequest* imgreq = image->GetImageData();
       nsCOMPtr<imgIContainer> image;
-      if (imgreq &&
-          NS_SUCCEEDED(imgreq->GetImage(getter_AddRefs(image))) &&
-          image) {
+      if (NS_SUCCEEDED(imgreq->GetImage(getter_AddRefs(image))) && image) {
         bool animated = false;
         if (NS_SUCCEEDED(image->GetAnimated(&animated)) && animated) {
           return WHENEVER_POSSIBLE;
diff --git a/layout/generic/nsFrame.cpp b/layout/generic/nsFrame.cpp
index e86a0e65333d..1cf36c3e89cd 100644
--- a/layout/generic/nsFrame.cpp
+++ b/layout/generic/nsFrame.cpp
@@ -792,9 +792,8 @@ AddAndRemoveImageAssociations(nsFrame* aFrame,
           continue;
         }
 
-        if (imgRequestProxy* req = oldImage.GetImageData()) {
-          imageLoader->DisassociateRequestFromFrame(req, aFrame);
-        }
+        imageLoader->DisassociateRequestFromFrame(oldImage.GetImageData(),
+                                                   aFrame);
       }
     }
   }
@@ -809,9 +808,7 @@ AddAndRemoveImageAssociations(nsFrame* aFrame,
         continue;
       }
 
-      if (imgRequestProxy* req = newImage.GetImageData()) {
-        imageLoader->AssociateRequestToFrame(req, aFrame);
-      }
+      imageLoader->AssociateRequestToFrame(newImage.GetImageData(), aFrame);
     }
   }
 }
@@ -4303,11 +4300,7 @@ nsIFrame::AssociateImage(const nsStyleImage& aImage, nsPresContext* aPresContext
     return;
   }
 
-  imgRequestProxy* req = aImage.GetImageData();
-  if (!req) {
-    return;
-  }
-
+  imgIRequest *req = aImage.GetImageData();
   mozilla::css::ImageLoader* loader =
     aPresContext->Document()->StyleImageLoader();
 
diff --git a/layout/style/ServoBindings.cpp b/layout/style/ServoBindings.cpp
index e4c3ffee1310..34c86375d506 100644
--- a/layout/style/ServoBindings.cpp
+++ b/layout/style/ServoBindings.cpp
@@ -734,45 +734,6 @@ Gecko_SetGradientImageValue(nsStyleImage* aImage, nsStyleGradient* aGradient)
   aImage->SetGradientData(aGradient);
 }
 
-static already_AddRefed<nsStyleImageRequest>
-CreateStyleImageRequest(nsStyleImageRequest::Mode aModeFlags,
-                        const uint8_t* aURLString, uint32_t aURLStringLength,
-                        ThreadSafeURIHolder* aBaseURI,
-                        ThreadSafeURIHolder* aReferrer,
-                        ThreadSafePrincipalHolder* aPrincipal)
-{
-  MOZ_ASSERT(aURLString);
-  MOZ_ASSERT(aBaseURI);
-  MOZ_ASSERT(aReferrer);
-  MOZ_ASSERT(aPrincipal);
-
-  nsString url;
-  nsDependentCSubstring urlString(reinterpret_cast<const char*>(aURLString),
-                                  aURLStringLength);
-  AppendUTF8toUTF16(urlString, url);
-  RefPtr<nsStringBuffer> urlBuffer = nsCSSValue::BufferFromString(url);
-
-  RefPtr<nsStyleImageRequest> req =
-    new nsStyleImageRequest(aModeFlags, urlBuffer, do_AddRef(aBaseURI),
-                            do_AddRef(aReferrer), do_AddRef(aPrincipal));
-  return req.forget();
-}
-
-void
-Gecko_SetUrlImageValue(nsStyleImage* aImage,
-                       const uint8_t* aURLString, uint32_t aURLStringLength,
-                       ThreadSafeURIHolder* aBaseURI,
-                       ThreadSafeURIHolder* aReferrer,
-                       ThreadSafePrincipalHolder* aPrincipal)
-{
-  RefPtr<nsStyleImageRequest> req =
-    CreateStyleImageRequest(nsStyleImageRequest::Mode::Track |
-                            nsStyleImageRequest::Mode::Lock,
-                            aURLString, aURLStringLength,
-                            aBaseURI, aReferrer, aPrincipal);
-  aImage->SetImageRequest(req.forget());
-}
-
 void
 Gecko_CopyImageValueFrom(nsStyleImage* aImage, const nsStyleImage* aOther)
 {
@@ -814,32 +775,6 @@ Gecko_CreateGradient(uint8_t aShape,
   return result;
 }
 
-void
-Gecko_SetListStyleImageNone(nsStyleList* aList)
-{
-  aList->mListStyleImage = nullptr;
-}
-
-void
-Gecko_SetListStyleImage(nsStyleList* aList,
-                        const uint8_t* aURLString, uint32_t aURLStringLength,
-                        ThreadSafeURIHolder* aBaseURI,
-                        ThreadSafeURIHolder* aReferrer,
-                        ThreadSafePrincipalHolder* aPrincipal)
-{
-  aList->mListStyleImage =
-    CreateStyleImageRequest(nsStyleImageRequest::Mode::Track |
-                            nsStyleImageRequest::Mode::Lock,
-                            aURLString, aURLStringLength,
-                            aBaseURI, aReferrer, aPrincipal);
-}
-
-void
-Gecko_CopyListStyleImageFrom(nsStyleList* aList, const nsStyleList* aSource)
-{
-  aList->mListStyleImage = aSource->mListStyleImage;
-}
-
 void
 Gecko_EnsureTArrayCapacity(void* aArray, size_t aCapacity, size_t aElemSize)
 {
diff --git a/layout/style/ServoBindings.h b/layout/style/ServoBindings.h
index 78b8a554dede..71079b72a15e 100644
--- a/layout/style/ServoBindings.h
+++ b/layout/style/ServoBindings.h
@@ -156,10 +156,6 @@ DECL_BORROWED_MUT_REF_TYPE_FOR(StyleChildrenIterator)
 
 extern "C" {
 
-// Object refcounting.
-NS_DECL_HOLDER_FFI_REFCOUNTING(nsIPrincipal, Principal)
-NS_DECL_HOLDER_FFI_REFCOUNTING(nsIURI, URI)
-
 // DOM Traversal.
 uint32_t Gecko_ChildrenCount(RawGeckoNodeBorrowed node);
 bool Gecko_NodeIsElement(RawGeckoNodeBorrowed node);
@@ -250,15 +246,9 @@ void Gecko_SetListStyleType(nsStyleList* style_struct, uint32_t type);
 void Gecko_CopyListStyleTypeFrom(nsStyleList* dst, const nsStyleList* src);
 
 // background-image style.
-// TODO: support element() and -moz-image()
+// TODO: support url() values (and maybe element() too?).
 void Gecko_SetNullImageValue(nsStyleImage* image);
 void Gecko_SetGradientImageValue(nsStyleImage* image, nsStyleGradient* gradient);
-void Gecko_SetUrlImageValue(nsStyleImage* image,
-                            const uint8_t* url_bytes,
-                            uint32_t url_length,
-                            ThreadSafeURIHolder* base_uri,
-                            ThreadSafeURIHolder* referrer,
-                            ThreadSafePrincipalHolder* principal);
 void Gecko_CopyImageValueFrom(nsStyleImage* image, const nsStyleImage* other);
 
 nsStyleGradient* Gecko_CreateGradient(uint8_t shape,
@@ -267,14 +257,9 @@ nsStyleGradient* Gecko_CreateGradient(uint8_t shape,
                                       bool legacy_syntax,
                                       uint32_t stops);
 
-// list-style-image style.
-void Gecko_SetListStyleImageNone(nsStyleList* style_struct);
-void Gecko_SetListStyleImage(nsStyleList* style_struct,
-                             const uint8_t* string_bytes, uint32_t string_length,
-                             ThreadSafeURIHolder* base_uri,
-                             ThreadSafeURIHolder* referrer,
-                             ThreadSafePrincipalHolder* principal);
-void Gecko_CopyListStyleImageFrom(nsStyleList* dest, const nsStyleList* src);
+// Object refcounting.
+NS_DECL_HOLDER_FFI_REFCOUNTING(nsIPrincipal, Principal)
+NS_DECL_HOLDER_FFI_REFCOUNTING(nsIURI, URI)
 
 // Display style.
 void Gecko_SetMozBinding(nsStyleDisplay* style_struct,
diff --git a/layout/style/nsCSSValue.cpp b/layout/style/nsCSSValue.cpp
index 9f6553179724..c52ca102afe4 100644
--- a/layout/style/nsCSSValue.cpp
+++ b/layout/style/nsCSSValue.cpp
@@ -25,7 +25,6 @@
 #include "nsStyleUtil.h"
 #include "nsDeviceContext.h"
 #include "nsStyleSet.h"
-#include "nsContentUtils.h"
 
 using namespace mozilla;
 
@@ -366,17 +365,6 @@ imgRequestProxy* nsCSSValue::GetImageValue(nsIDocument* aDocument) const
   return mValue.mImage->mRequests.GetWeak(aDocument);
 }
 
-already_AddRefed<imgRequestProxy>
-nsCSSValue::GetPossiblyStaticImageValue(nsIDocument* aDocument,
-                                        nsPresContext* aPresContext) const
-{
-  imgRequestProxy* req = GetImageValue(aDocument);
-  if (aPresContext->IsDynamic()) {
-    return do_AddRef(req);
-  }
-  return nsContentUtils::GetStaticRequest(req);
-}
-
 nscoord nsCSSValue::GetFixedLength(nsPresContext* aPresContext) const
 {
   MOZ_ASSERT(mUnit == eCSSUnit_PhysicalMillimeter,
@@ -2878,25 +2866,8 @@ css::ImageValue::ImageValue(nsIURI* aURI, nsStringBuffer* aString,
                  do_AddRef(new PtrHolder<nsIURI>(aBaseURI, false)),
                  do_AddRef(new PtrHolder<nsIURI>(aReferrer)),
                  do_AddRef(new PtrHolder<nsIPrincipal>(aOriginPrincipal)))
-{
-  Initialize(aDocument);
-}
-
-css::ImageValue::ImageValue(
-    nsStringBuffer* aString,
-    already_AddRefed<PtrHolder<nsIURI>> aBaseURI,
-    already_AddRefed<PtrHolder<nsIURI>> aReferrer,
-    already_AddRefed<PtrHolder<nsIPrincipal>> aOriginPrincipal)
-  : URLValueData(aString, Move(aBaseURI), Move(aReferrer),
-                 Move(aOriginPrincipal))
-{
-}
-
-void
-css::ImageValue::Initialize(nsIDocument* aDocument)
 {
   MOZ_ASSERT(NS_IsMainThread());
-  MOZ_ASSERT(!mInitialized);
 
   // NB: If aDocument is not the original document, we may not be able to load
   // images from aDocument.  Instead we do the image load from the original doc
@@ -2906,16 +2877,12 @@ css::ImageValue::Initialize(nsIDocument* aDocument)
     loadingDoc = aDocument;
   }
 
-  loadingDoc->StyleImageLoader()->LoadImage(GetURI(), mOriginPrincipal,
-                                            mReferrer, this);
+  loadingDoc->StyleImageLoader()->LoadImage(aURI, aOriginPrincipal, aReferrer,
+                                            this);
 
   if (loadingDoc != aDocument) {
     aDocument->StyleImageLoader()->MaybeRegisterCSSImage(this);
   }
-
-#ifdef DEBUG
-  mInitialized = true;
-#endif
 }
 
 css::ImageValue::~ImageValue()
diff --git a/layout/style/nsCSSValue.h b/layout/style/nsCSSValue.h
index 0e7f18c7f87a..be3efbb36934 100644
--- a/layout/style/nsCSSValue.h
+++ b/layout/style/nsCSSValue.h
@@ -208,18 +208,9 @@ struct ImageValue final : public URLValueData
              nsIURI* aReferrer, nsIPrincipal* aOriginPrincipal,
              nsIDocument* aDocument);
 
-  // This constructor is safe to call from any thread, but Initialize
-  // must be called later for the object to be useful.
-  ImageValue(nsStringBuffer* aString,
-             already_AddRefed<PtrHolder<nsIURI>> aBaseURI,
-             already_AddRefed<PtrHolder<nsIURI>> aReferrer,
-             already_AddRefed<PtrHolder<nsIPrincipal>> aOriginPrincipal);
-
   ImageValue(const ImageValue&) = delete;
   ImageValue& operator=(const ImageValue&) = delete;
 
-  void Initialize(nsIDocument* aDocument);
-
   // XXXheycam We should have our own SizeOfIncludingThis method.
 
 protected:
@@ -229,11 +220,6 @@ public:
   // Inherit Equals from URLValueData
 
   nsRefPtrHashtable<nsPtrHashKey<nsIDocument>, imgRequestProxy> mRequests;
-
-private:
-#ifdef DEBUG
-  bool mInitialized = false;
-#endif
 };
 
 struct GridNamedArea {
@@ -869,11 +855,6 @@ public:
   // all over.
   imgRequestProxy* GetImageValue(nsIDocument* aDocument) const;
 
-  // Like GetImageValue, but additionally will pass the imgRequestProxy
-  // through nsContentUtils::GetStaticRequest if aPresContent is static.
-  already_AddRefed<imgRequestProxy> GetPossiblyStaticImageValue(
-      nsIDocument* aDocument, nsPresContext* aPresContext) const;
-
   nscoord GetFixedLength(nsPresContext* aPresContext) const;
   nscoord GetPixelLength() const;
 
diff --git a/layout/style/nsComputedDOMStyle.cpp b/layout/style/nsComputedDOMStyle.cpp
index 504e562c7c59..4244658d580b 100644
--- a/layout/style/nsComputedDOMStyle.cpp
+++ b/layout/style/nsComputedDOMStyle.cpp
@@ -2082,15 +2082,7 @@ nsComputedDOMStyle::SetValueToStyleImage(const nsStyleImage& aStyleImage,
   switch (aStyleImage.GetType()) {
     case eStyleImageType_Image:
     {
-      imgIRequest* req = aStyleImage.GetImageData();
-      if (!req) {
-        // XXXheycam If we had some problem resolving the imgRequestProxy,
-        // maybe we should just use the URL stored in the nsStyleImage's
-        // mImageValue?  (Similarly in DoGetListStyleImage.)
-        aValue->SetIdent(eCSSKeyword_none);
-        break;
-      }
-
+      imgIRequest *req = aStyleImage.GetImageData();
       nsCOMPtr<nsIURI> uri;
       req->GetURI(getter_AddRefs(uri));
 
@@ -3503,16 +3495,13 @@ nsComputedDOMStyle::DoGetListStyleImage()
 
   const nsStyleList* list = StyleList();
 
-  // XXXheycam As in SetValueToStyleImage, we might want to use the
-  // URL stored in the nsStyleImageRequest's mImageValue if we
-  // failed to resolve the imgRequestProxy.
-
-  imgRequestProxy* image = list->GetListStyleImage();
-  if (!image) {
+  if (!list->GetListStyleImage()) {
     val->SetIdent(eCSSKeyword_none);
   } else {
     nsCOMPtr<nsIURI> uri;
-    image->GetURI(getter_AddRefs(uri));
+    if (list->GetListStyleImage()) {
+      list->GetListStyleImage()->GetURI(getter_AddRefs(uri));
+    }
     val->SetURI(uri);
   }
 
diff --git a/layout/style/nsRuleNode.cpp b/layout/style/nsRuleNode.cpp
index b1e03b94a36b..5b133cadfcbb 100644
--- a/layout/style/nsRuleNode.cpp
+++ b/layout/style/nsRuleNode.cpp
@@ -128,30 +128,13 @@ SetImageRequest(function<void(imgRequestProxy*)> aCallback,
                 nsPresContext* aPresContext,
                 const nsCSSValue& aValue)
 {
-  RefPtr<imgRequestProxy> req =
-    aValue.GetPossiblyStaticImageValue(aPresContext->Document(),
-                                       aPresContext);
-  aCallback(req);
-}
-
-static void
-SetStyleImageRequest(function<void(nsStyleImageRequest*)> aCallback,
-                     nsPresContext* aPresContext,
-                     const nsCSSValue& aValue,
-                     nsStyleImageRequest::Mode aModeFlags =
-                       nsStyleImageRequest::Mode::Track |
-                       nsStyleImageRequest::Mode::Lock)
-{
-  SetImageRequest([&](imgRequestProxy* aProxy) {
-    RefPtr<nsStyleImageRequest> request;
-    if (aProxy) {
-      css::ImageValue* imageValue = aValue.GetImageStructValue();
-      ImageTracker* imageTracker = aPresContext->Document()->ImageTracker();
-      request =
-        new nsStyleImageRequest(aModeFlags, aProxy, imageValue, imageTracker);
-    }
-    aCallback(request);
-  }, aPresContext, aValue);
+  imgRequestProxy* req = GetImageRequest(aPresContext, aValue);
+  if (aPresContext->IsDynamic()) {
+    aCallback(req);
+  } else {
+    RefPtr<imgRequestProxy> staticReq = nsContentUtils::GetStaticRequest(req);
+    aCallback(staticReq);
+  }
 }
 
 template<typename ReferenceBox>
@@ -1284,8 +1267,8 @@ static void SetStyleImageToImageRect(nsStyleContext* aStyleContext,
 
   // <uri>
   if (arr->Item(1).GetUnit() == eCSSUnit_Image) {
-    SetStyleImageRequest([&](nsStyleImageRequest* req) {
-      aResult.SetImageRequest(do_AddRef(req));
+    SetImageRequest([&](imgRequestProxy* req) {
+      aResult.SetImageData(req);
     }, aStyleContext->PresContext(), arr->Item(1));
   } else {
     NS_WARNING("nsCSSValue::Image::Image() failed?");
@@ -1320,8 +1303,8 @@ static void SetStyleImage(nsStyleContext* aStyleContext,
 
   switch (aValue.GetUnit()) {
     case eCSSUnit_Image:
-      SetStyleImageRequest([&](nsStyleImageRequest* req) {
-        aResult.SetImageRequest(do_AddRef(req));
+      SetImageRequest([&](imgRequestProxy* req) {
+        aResult.SetImageData(req);
       }, aStyleContext->PresContext(), aValue);
       break;
     case eCSSUnit_Function:
@@ -7345,6 +7328,9 @@ nsRuleNode::ComputeBackgroundData(void* aStartStruct,
     FillAllBackgroundLists(bg->mImage, maxItemCount);
   }
 
+  // Now that the dust has settled, register the images with the document
+  bg->mImage.TrackImages(aContext->PresContext());
+
   COMPUTE_END_RESET(Background, bg)
 }
 
@@ -7731,6 +7717,8 @@ nsRuleNode::ComputeBorderData(void* aStartStruct,
            parentBorder->mBorderImageRepeatV,
            NS_STYLE_BORDER_IMAGE_REPEAT_STRETCH);
 
+  border->TrackImage(aContext->PresContext());
+
   COMPUTE_END_RESET(Border, border)
 }
 
@@ -7963,18 +7951,18 @@ nsRuleNode::ComputeListData(void* aStartStruct,
   // list-style-image: url, none, inherit
   const nsCSSValue* imageValue = aRuleData->ValueForListStyleImage();
   if (eCSSUnit_Image == imageValue->GetUnit()) {
-    SetStyleImageRequest([&](nsStyleImageRequest* req) {
-      list->mListStyleImage = req;
+    SetImageRequest([&](imgRequestProxy* req) {
+      list->SetListStyleImage(req);
     }, mPresContext, *imageValue);
   }
   else if (eCSSUnit_None == imageValue->GetUnit() ||
            eCSSUnit_Initial == imageValue->GetUnit()) {
-    list->mListStyleImage = nullptr;
+    list->SetListStyleImage(nullptr);
   }
   else if (eCSSUnit_Inherit == imageValue->GetUnit() ||
            eCSSUnit_Unset == imageValue->GetUnit()) {
     conditions.SetUncacheable();
-    list->mListStyleImage = parentList->mListStyleImage;
+    list->SetListStyleImage(parentList->GetListStyleImage());
   }
 
   // list-style-position: enum, inherit, initial
@@ -8997,8 +8985,7 @@ nsRuleNode::ComputeContentData(void* aStartStruct,
   for (uint32_t i = 0; i < content->ContentCount(); ++i) {
     if ((content->ContentAt(i).mType == eStyleContentType_Image) &&
         content->ContentAt(i).mContent.mImage) {
-      content->ContentAt(i).TrackImage(
-          aContext->PresContext()->Document()->ImageTracker());
+      content->ContentAt(i).TrackImage(aContext->PresContext());
     }
   }
 
@@ -10067,6 +10054,8 @@ nsRuleNode::ComputeSVGResetData(void* aStartStruct,
   }
 #endif
 
+  svgReset->mMask.TrackImages(aContext->PresContext());
+
   COMPUTE_END_RESET(SVGReset, svgReset)
 }
 
diff --git a/layout/style/nsStyleContext.cpp b/layout/style/nsStyleContext.cpp
index e82dd3ec4bfb..56563597cba5 100644
--- a/layout/style/nsStyleContext.cpp
+++ b/layout/style/nsStyleContext.cpp
@@ -468,24 +468,8 @@ const void* nsStyleContext::StyleData(nsStyleStructID aSID)
       mCachedInheritedData.mStyleStructs[aSID] = const_cast<void*>(newData);
     }
   } else {
-    newData = StyleStructFromServoComputedValues(aSID);
-
-    // perform any remaining main thread work on the struct
-    switch (aSID) {
-#define STYLE_STRUCT(name_, checkdata_cb_)                                    \
-      case eStyleStruct_##name_: {                                            \
-        auto data = static_cast<const nsStyle##name_*>(newData);              \
-        const_cast<nsStyle##name_*>(data)->FinishStyle(PresContext());        \
-        break;                                                                \
-      }
-#include "nsStyleStructList.h"
-#undef STYLE_STRUCT
-      default:
-        MOZ_ASSERT_UNREACHABLE("unexpected nsStyleStructID value");
-        break;
-    }
-
     // The Servo-backed StyleContextSource owns the struct.
+    newData = StyleStructFromServoComputedValues(aSID);
     AddStyleBit(nsCachedStyleData::GetBitForSID(aSID));
 
     // XXXbholley: Unconditionally caching reset structs here defeats the memory
diff --git a/layout/style/nsStyleContext.h b/layout/style/nsStyleContext.h
index cb76b81f1265..6d641ac175fd 100644
--- a/layout/style/nsStyleContext.h
+++ b/layout/style/nsStyleContext.h
@@ -673,8 +673,6 @@ private:
           newData =                                                     \
             Servo_GetStyle##name_(mSource.AsServoComputedValues());     \
         }                                                               \
-        /* perform any remaining main thread work on the struct */      \
-        const_cast<nsStyle##name_*>(newData)->FinishStyle(PresContext());\
         /* the Servo-backed StyleContextSource owns the struct */       \
         AddStyleBit(NS_STYLE_INHERIT_BIT(name_));                       \
       }                                                                 \
@@ -703,8 +701,6 @@ private:
       } else {                                                          \
         newData =                                                       \
           Servo_GetStyle##name_(mSource.AsServoComputedValues());       \
-        /* perform any remaining main thread work on the struct */      \
-        const_cast<nsStyle##name_*>(newData)->FinishStyle(PresContext());\
         /* The Servo-backed StyleContextSource owns the struct.         \
          *                                                              \
          * XXXbholley: Unconditionally caching reset structs here       \
diff --git a/layout/style/nsStyleStruct.cpp b/layout/style/nsStyleStruct.cpp
index 8d387b0a58d3..70a8bb6f2cd3 100644
--- a/layout/style/nsStyleStruct.cpp
+++ b/layout/style/nsStyleStruct.cpp
@@ -93,21 +93,6 @@ EqualImages(imgIRequest *aImage1, imgIRequest* aImage2)
   return EqualURIs(uri1, uri2);
 }
 
-static bool
-DefinitelyEqualImages(nsStyleImageRequest* aRequest1,
-                      nsStyleImageRequest* aRequest2)
-{
-  if (aRequest1 == aRequest2) {
-    return true;
-  }
-
-  if (!aRequest1 || !aRequest2) {
-    return false;
-  }
-
-  return aRequest1->DefinitelyEquals(*aRequest2);
-}
-
 // A nullsafe wrapper for strcmp. We depend on null-safety.
 static int
 safe_strcmp(const char16_t* a, const char16_t* b)
@@ -451,15 +436,6 @@ nsStyleBorder::~nsStyleBorder()
   }
 }
 
-void
-nsStyleBorder::FinishStyle(nsPresContext* aPresContext)
-{
-  MOZ_ASSERT(NS_IsMainThread());
-  MOZ_ASSERT(aPresContext->StyleSet()->IsServo());
-
-  mBorderImageSource.ResolveImage(aPresContext);
-}
-
 nsMargin
 nsStyleBorder::GetImageOutset() const
 {
@@ -488,8 +464,8 @@ nsStyleBorder::GetImageOutset() const
 }
 
 void
-nsStyleBorder::Destroy(nsPresContext* aContext)
-{
+nsStyleBorder::Destroy(nsPresContext* aContext) {
+  UntrackImage(aContext);
   this->~nsStyleBorder();
   aContext->PresShell()->
     FreeByObjectID(eArenaObjectID_nsStyleBorder, this);
@@ -666,25 +642,14 @@ nsStyleList::~nsStyleList()
 
 nsStyleList::nsStyleList(const nsStyleList& aSource)
   : mListStylePosition(aSource.mListStylePosition)
-  , mListStyleImage(aSource.mListStyleImage)
   , mCounterStyle(aSource.mCounterStyle)
   , mQuotes(aSource.mQuotes)
   , mImageRegion(aSource.mImageRegion)
 {
+  SetListStyleImage(aSource.GetListStyleImage());
   MOZ_COUNT_CTOR(nsStyleList);
 }
 
-void
-nsStyleList::FinishStyle(nsPresContext* aPresContext)
-{
-  MOZ_ASSERT(NS_IsMainThread());
-  MOZ_ASSERT(aPresContext->StyleSet()->IsServo());
-
-  if (mListStyleImage && !mListStyleImage->IsResolved()) {
-    mListStyleImage->Resolve(aPresContext);
-  }
-}
-
 void
 nsStyleList::SetQuotesInherit(const nsStyleList* aOther)
 {
@@ -749,7 +714,7 @@ nsStyleList::CalcDifference(const nsStyleList& aNewData) const
   if (mListStylePosition != aNewData.mListStylePosition) {
     return nsChangeHint_ReconstructFrame;
   }
-  if (DefinitelyEqualImages(mListStyleImage, aNewData.mListStyleImage) &&
+  if (EqualImages(mListStyleImage, aNewData.mListStyleImage) &&
       mCounterStyle == aNewData.mCounterStyle) {
     if (mImageRegion.IsEqualInterior(aNewData.mImageRegion)) {
       return nsChangeHint(0);
@@ -1204,20 +1169,13 @@ nsStyleSVGReset::nsStyleSVGReset(const nsStyleSVGReset& aSource)
 void
 nsStyleSVGReset::Destroy(nsPresContext* aContext)
 {
+  mMask.UntrackImages(aContext);
+
   this->~nsStyleSVGReset();
   aContext->PresShell()->
     FreeByObjectID(mozilla::eArenaObjectID_nsStyleSVGReset, this);
 }
 
-void
-nsStyleSVGReset::FinishStyle(nsPresContext* aPresContext)
-{
-  MOZ_ASSERT(NS_IsMainThread());
-  MOZ_ASSERT(aPresContext->StyleSet()->IsServo());
-
-  mMask.ResolveImages(aPresContext);
-}
-
 nsChangeHint
 nsStyleSVGReset::CalcDifference(const nsStyleSVGReset& aNewData) const
 {
@@ -1911,174 +1869,6 @@ nsStyleGradient::HasCalc()
          mRadiusX.IsCalcUnit() || mRadiusY.IsCalcUnit();
 }
 
-
-// --------------------
-// nsStyleImageRequest
-
-/**
- * Runnable to release the nsStyleImageRequest's mRequestProxy,
- * mImageValue and mImageValue on the main thread, and to perform
- * any necessary unlocking and untracking of the image.
- */
-class StyleImageRequestCleanupTask : public mozilla::Runnable
-{
-public:
-  typedef nsStyleImageRequest::Mode Mode;
-
-  StyleImageRequestCleanupTask(Mode aModeFlags,
-                               already_AddRefed<imgRequestProxy> aRequestProxy,
-                               already_AddRefed<css::ImageValue> aImageValue,
-                               already_AddRefed<ImageTracker> aImageTracker)
-    : mModeFlags(aModeFlags)
-    , mRequestProxy(aRequestProxy)
-    , mImageValue(aImageValue)
-    , mImageTracker(aImageTracker)
-  {
-  }
-
-  NS_IMETHOD Run() final
-  {
-    MOZ_ASSERT(NS_IsMainThread());
-
-    if (!mRequestProxy) {
-      return NS_OK;
-    }
-
-    MOZ_ASSERT(mImageTracker);
-
-    if (mModeFlags & Mode::Lock) {
-      mRequestProxy->UnlockImage();
-    }
-
-    if (mModeFlags & Mode::Discard) {
-      mRequestProxy->RequestDiscard();
-    }
-
-    if (mModeFlags & Mode::Track) {
-      mImageTracker->Remove(mRequestProxy);
-    }
-
-    return NS_OK;
-  }
-
-protected:
-  virtual ~StyleImageRequestCleanupTask() { MOZ_ASSERT(NS_IsMainThread()); }
-
-private:
-  Mode mModeFlags;
-  // Since we always dispatch this runnable to the main thread, these will be
-  // released on the main thread when the runnable itself is released.
-  RefPtr<imgRequestProxy> mRequestProxy;
-  RefPtr<css::ImageValue> mImageValue;
-  RefPtr<ImageTracker> mImageTracker;
-};
-
-nsStyleImageRequest::nsStyleImageRequest(Mode aModeFlags,
-                                         imgRequestProxy* aRequestProxy,
-                                         css::ImageValue* aImageValue,
-                                         ImageTracker* aImageTracker)
-  : mRequestProxy(aRequestProxy)
-  , mImageValue(aImageValue)
-  , mImageTracker(aImageTracker)
-  , mModeFlags(aModeFlags)
-  , mResolved(true)
-{
-  MOZ_ASSERT(NS_IsMainThread());
-  MOZ_ASSERT(aRequestProxy);
-  MOZ_ASSERT(aImageValue);
-  MOZ_ASSERT(aImageTracker);
-
-  MaybeTrackAndLock();
-}
-
-nsStyleImageRequest::nsStyleImageRequest(
-    Mode aModeFlags,
-    nsStringBuffer* aURLBuffer,
-    already_AddRefed<PtrHolder<nsIURI>> aBaseURI,
-    already_AddRefed<PtrHolder<nsIURI>> aReferrer,
-    already_AddRefed<PtrHolder<nsIPrincipal>> aPrincipal)
-  : mModeFlags(aModeFlags)
-  , mResolved(false)
-{
-  mImageValue = new css::ImageValue(aURLBuffer, Move(aBaseURI),
-                                    Move(aReferrer), Move(aPrincipal));
-}
-
-nsStyleImageRequest::~nsStyleImageRequest()
-{
-  // We may or may not be being destroyed on the main thread.  To clean
-  // up, we must untrack and unlock the image (depending on mModeFlags),
-  // and release mRequestProxy and mImageValue, all on the main thread.
-  {
-    RefPtr<StyleImageRequestCleanupTask> task =
-        new StyleImageRequestCleanupTask(mModeFlags,
-                                         mRequestProxy.forget(),
-                                         mImageValue.forget(),
-                                         mImageTracker.forget());
-    if (NS_IsMainThread()) {
-      task->Run();
-    } else {
-      NS_DispatchToMainThread(task.forget());
-    }
-  }
-
-  MOZ_ASSERT(!mRequestProxy);
-  MOZ_ASSERT(!mImageValue);
-  MOZ_ASSERT(!mImageTracker);
-}
-
-bool
-nsStyleImageRequest::Resolve(nsPresContext* aPresContext)
-{
-  MOZ_ASSERT(NS_IsMainThread());
-  MOZ_ASSERT(!IsResolved(), "already resolved");
-
-  mResolved = true;
-
-  // For now, just have unique nsCSSValue/ImageValue objects.  We should
-  // really store the ImageValue on the Servo specified value, so that we can
-  // share imgRequestProxys that come from the same rule in the same
-  // document.
-  mImageValue->Initialize(aPresContext->Document());
-
-  nsCSSValue value;
-  value.SetImageValue(mImageValue);
-  mRequestProxy = value.GetPossiblyStaticImageValue(aPresContext->Document(),
-                                                    aPresContext);
-
-  if (!mRequestProxy) {
-    // The URL resolution or image load failed.
-    return false;
-  }
-
-  mImageTracker = aPresContext->Document()->ImageTracker();
-  MaybeTrackAndLock();
-  return true;
-}
-
-void
-nsStyleImageRequest::MaybeTrackAndLock()
-{
-  MOZ_ASSERT(NS_IsMainThread());
-  MOZ_ASSERT(IsResolved());
-  MOZ_ASSERT(mRequestProxy);
-  MOZ_ASSERT(mImageTracker);
-
-  if (mModeFlags & Mode::Track) {
-    mImageTracker->Add(mRequestProxy);
-  }
-
-  if (mModeFlags & Mode::Lock) {
-    mRequestProxy->LockImage();
-  }
-}
-
-bool
-nsStyleImageRequest::DefinitelyEquals(const nsStyleImageRequest& aOther) const
-{
-  return DefinitelyEqualURIs(mImageValue, aOther.mImageValue);
-}
-
 // --------------------
 // CachedBorderImageData
 //
@@ -2123,6 +1913,9 @@ CachedBorderImageData::GetSubImage(uint8_t aIndex)
 nsStyleImage::nsStyleImage()
   : mType(eStyleImageType_Null)
   , mCropRect(nullptr)
+#ifdef DEBUG
+  , mImageTracked(false)
+#endif
 {
   MOZ_COUNT_CTOR(nsStyleImage);
 }
@@ -2138,6 +1931,9 @@ nsStyleImage::~nsStyleImage()
 nsStyleImage::nsStyleImage(const nsStyleImage& aOther)
   : mType(eStyleImageType_Null)
   , mCropRect(nullptr)
+#ifdef DEBUG
+  , mImageTracked(false)
+#endif
 {
   // We need our own copy constructor because we don't want
   // to copy the reference count
@@ -2161,7 +1957,7 @@ nsStyleImage::DoCopy(const nsStyleImage& aOther)
   SetNull();
 
   if (aOther.mType == eStyleImageType_Image) {
-    SetImageRequest(do_AddRef(aOther.mImage));
+    SetImageData(aOther.mImage);
   } else if (aOther.mType == eStyleImageType_Gradient) {
     SetGradientData(aOther.mGradient);
   } else if (aOther.mType == eStyleImageType_Element) {
@@ -2178,6 +1974,9 @@ nsStyleImage::DoCopy(const nsStyleImage& aOther)
 void
 nsStyleImage::SetNull()
 {
+  MOZ_ASSERT(!mImageTracked,
+             "Calling SetNull() with image tracked!");
+
   if (mType == eStyleImageType_Gradient) {
     mGradient->Release();
   } else if (mType == eStyleImageType_Image) {
@@ -2191,16 +1990,19 @@ nsStyleImage::SetNull()
 }
 
 void
-nsStyleImage::SetImageRequest(already_AddRefed<nsStyleImageRequest> aImage)
+nsStyleImage::SetImageData(imgRequestProxy* aImage)
 {
-  RefPtr<nsStyleImageRequest> image = aImage;
+  MOZ_ASSERT(!mImageTracked,
+             "Setting a new image without untracking the old one!");
+
+  NS_IF_ADDREF(aImage);
 
   if (mType != eStyleImageType_Null) {
     SetNull();
   }
 
-  if (image) {
-    mImage = image.forget().take();
+  if (aImage) {
+    mImage = aImage;
     mType = eStyleImageType_Image;
   }
   if (mCachedBIData) {
@@ -2208,6 +2010,46 @@ nsStyleImage::SetImageRequest(already_AddRefed<nsStyleImageRequest> aImage)
   }
 }
 
+void
+nsStyleImage::TrackImage(nsPresContext* aContext)
+{
+  // Sanity
+  MOZ_ASSERT(!mImageTracked, "Already tracking image!");
+  MOZ_ASSERT(mType == eStyleImageType_Image,
+             "Can't track image when there isn't one!");
+
+  // Register the image with the document
+  nsIDocument* doc = aContext->Document();
+  if (doc) {
+    doc->ImageTracker()->Add(mImage);
+  }
+
+  // Mark state
+#ifdef DEBUG
+  mImageTracked = true;
+#endif
+}
+
+void
+nsStyleImage::UntrackImage(nsPresContext* aContext)
+{
+  // Sanity
+  MOZ_ASSERT(mImageTracked, "Image not tracked!");
+  MOZ_ASSERT(mType == eStyleImageType_Image,
+             "Can't untrack image when there isn't one!");
+
+  // Unregister the image with the document
+  nsIDocument* doc = aContext->Document();
+  if (doc) {
+    doc->ImageTracker()->Remove(mImage);
+  }
+
+  // Mark state
+#ifdef DEBUG
+  mImageTracked = false;
+#endif
+}
+
 void
 nsStyleImage::SetGradientData(nsStyleGradient* aGradient)
 {
@@ -2272,13 +2114,8 @@ nsStyleImage::ComputeActualCropRect(nsIntRect& aActualCropRect,
     return false;
   }
 
-  imgRequestProxy* req = GetImageData();
-  if (!req) {
-    return false;
-  }
-
   nsCOMPtr<imgIContainer> imageContainer;
-  req->GetImage(getter_AddRefs(imageContainer));
+  mImage->GetImage(getter_AddRefs(imageContainer));
   if (!imageContainer) {
     return false;
   }
@@ -2310,11 +2147,7 @@ nsresult
 nsStyleImage::StartDecoding() const
 {
   if (mType == eStyleImageType_Image) {
-    imgRequestProxy* req = GetImageData();
-    if (!req) {
-      return NS_ERROR_FAILURE;
-    }
-    return req->StartDecoding();
+    return mImage->StartDecoding();
   }
   return NS_OK;
 }
@@ -2335,10 +2168,9 @@ nsStyleImage::IsOpaque() const
   }
 
   MOZ_ASSERT(mType == eStyleImageType_Image, "unexpected image type");
-  MOZ_ASSERT(GetImageData(), "should've returned earlier above");
 
   nsCOMPtr<imgIContainer> imageContainer;
-  GetImageData()->GetImage(getter_AddRefs(imageContainer));
+  mImage->GetImage(getter_AddRefs(imageContainer));
   MOZ_ASSERT(imageContainer, "IsComplete() said image container is ready");
 
   // Check if the crop region of the image is opaque.
@@ -2367,13 +2199,10 @@ nsStyleImage::IsComplete() const
     case eStyleImageType_Gradient:
     case eStyleImageType_Element:
       return true;
-    case eStyleImageType_Image: {
-      imgRequestProxy* req = GetImageData();
-      if (!req) {
-        return false;
-      }
+    case eStyleImageType_Image:
+    {
       uint32_t status = imgIRequest::STATUS_ERROR;
-      return NS_SUCCEEDED(req->GetImageStatus(&status)) &&
+      return NS_SUCCEEDED(mImage->GetImageStatus(&status)) &&
              (status & imgIRequest::STATUS_SIZE_AVAILABLE) &&
              (status & imgIRequest::STATUS_FRAME_COMPLETE);
     }
@@ -2392,13 +2221,10 @@ nsStyleImage::IsLoaded() const
     case eStyleImageType_Gradient:
     case eStyleImageType_Element:
       return true;
-    case eStyleImageType_Image: {
-      imgRequestProxy* req = GetImageData();
-      if (!req) {
-        return false;
-      }
+    case eStyleImageType_Image:
+    {
       uint32_t status = imgIRequest::STATUS_ERROR;
-      return NS_SUCCEEDED(req->GetImageStatus(&status)) &&
+      return NS_SUCCEEDED(mImage->GetImageStatus(&status)) &&
              !(status & imgIRequest::STATUS_ERROR) &&
              (status & imgIRequest::STATUS_LOAD_COMPLETE);
     }
@@ -2427,7 +2253,7 @@ nsStyleImage::operator==(const nsStyleImage& aOther) const
   }
 
   if (mType == eStyleImageType_Image) {
-    return DefinitelyEqualImages(mImage, aOther.mImage);
+    return EqualImages(mImage, aOther.mImage);
   }
 
   if (mType == eStyleImageType_Gradient) {
@@ -2708,9 +2534,7 @@ nsStyleImageLayers::Size::DependsOnPositioningAreaSize(const nsStyleImage& aImag
 
   if (type == eStyleImageType_Image) {
     nsCOMPtr<imgIContainer> imgContainer;
-    if (imgRequestProxy* req = aImage.GetImageData()) {
-      req->GetImage(getter_AddRefs(imgContainer));
-    }
+    aImage.GetImageData()->GetImage(getter_AddRefs(imgContainer));
     if (imgContainer) {
       CSSIntSize imageSize;
       nsSize imageRatio;
@@ -2944,20 +2768,14 @@ nsStyleBackground::~nsStyleBackground()
 void
 nsStyleBackground::Destroy(nsPresContext* aContext)
 {
+  // Untrack all the images stored in our layers
+  mImage.UntrackImages(aContext);
+
   this->~nsStyleBackground();
   aContext->PresShell()->
     FreeByObjectID(eArenaObjectID_nsStyleBackground, this);
 }
 
-void
-nsStyleBackground::FinishStyle(nsPresContext* aPresContext)
-{
-  MOZ_ASSERT(NS_IsMainThread());
-  MOZ_ASSERT(aPresContext->StyleSet()->IsServo());
-
-  mImage.ResolveImages(aPresContext);
-}
-
 nsChangeHint
 nsStyleBackground::CalcDifference(const nsStyleBackground& aNewData) const
 {
@@ -3609,7 +3427,7 @@ nsStyleContentData::operator==(const nsStyleContentData& aOther) const
 }
 
 void
-nsStyleContentData::TrackImage(ImageTracker* aImageTracker)
+nsStyleContentData::TrackImage(nsPresContext* aContext)
 {
   // Sanity
   MOZ_ASSERT(!mImageTracked, "Already tracking image!");
@@ -3618,7 +3436,11 @@ nsStyleContentData::TrackImage(ImageTracker* aImageTracker)
   MOZ_ASSERT(mContent.mImage,
              "Can't track image when there isn't one!");
 
-  aImageTracker->Add(mContent.mImage);
+  // Register the image with the document
+  nsIDocument* doc = aContext->Document();
+  if (doc) {
+    doc->ImageTracker()->Add(mContent.mImage);
+  }
 
   // Mark state
 #ifdef DEBUG
@@ -3627,7 +3449,7 @@ nsStyleContentData::TrackImage(ImageTracker* aImageTracker)
 }
 
 void
-nsStyleContentData::UntrackImage(ImageTracker* aImageTracker)
+nsStyleContentData::UntrackImage(nsPresContext* aContext)
 {
   // Sanity
   MOZ_ASSERT(mImageTracked, "Image not tracked!");
@@ -3636,7 +3458,11 @@ nsStyleContentData::UntrackImage(ImageTracker* aImageTracker)
   MOZ_ASSERT(mContent.mImage,
              "Can't untrack image when there isn't one!");
 
-  aImageTracker->Remove(mContent.mImage);
+  // Unregister the image with the document
+  nsIDocument* doc = aContext->Document();
+  if (doc) {
+    doc->ImageTracker()->Remove(mContent.mImage);
+  }
 
   // Mark state
 #ifdef DEBUG
@@ -3666,7 +3492,7 @@ nsStyleContent::Destroy(nsPresContext* aContext)
   // Unregister any images we might have with the document.
   for (auto& content : mContents) {
     if (content.mType == eStyleContentType_Image && content.mContent.mImage) {
-      content.UntrackImage(aContext->Document()->ImageTracker());
+      content.UntrackImage(aContext);
     }
   }
 
diff --git a/layout/style/nsStyleStruct.h b/layout/style/nsStyleStruct.h
index 34be357dc814..41ad9794cf22 100644
--- a/layout/style/nsStyleStruct.h
+++ b/layout/style/nsStyleStruct.h
@@ -46,11 +46,6 @@ class nsStyleContext;
 class nsTextFrame;
 class imgIContainer;
 struct nsStyleVisibility;
-namespace mozilla {
-namespace dom {
-class ImageTracker;
-} // namespace dom
-} // namespace mozilla
 
 typedef nsINode RawGeckoNode;
 typedef mozilla::dom::Element RawGeckoElement;
@@ -166,7 +161,6 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleFont
   ~nsStyleFont() {
     MOZ_COUNT_DTOR(nsStyleFont);
   }
-  void FinishStyle(nsPresContext* aPresContext) {}
 
   nsChangeHint CalcDifference(const nsStyleFont& aNewData) const;
   static nsChangeHint MaxDifference() {
@@ -288,97 +282,6 @@ private:
   nsStyleGradient& operator=(const nsStyleGradient& aOther) = delete;
 };
 
-/**
- * A wrapper for an imgRequestProxy that supports off-main-thread creation
- * and equality comparison.
- *
- * An nsStyleImageRequest can be created in two ways:
- *
- * 1. Using the constructor that takes an imgRequestProxy.  This must
- *    be called from the main thread.  The nsStyleImageRequest is
- *    immediately considered "resolved", and the get() method that
- *    returns the imgRequestProxy can be called.
- *
- * 2. Using the constructor that takes the URL, base URI, referrer
- *    and principal that can be used to inititiate an image load and
- *    produce an imgRequestProxy later.  This can be called from
- *    any thread.  The nsStyleImageRequest is not considered "resolved"
- *    at this point, and the Resolve() method must be called later
- *    to initiate the image load and make calls to get() valid.
- *
- * Calls to TrackImage(), UntrackImage(), LockImage(), UnlockImage() and
- * RequestDiscard() are made to the imgRequestProxy and ImageTracker as
- * appropriate, according to the mode flags passed in to the constructor.
- *
- * The main thread constructor takes a pointer to the css::ImageValue that
- * is the specified url() value, while the off-main-thread constructor
- * creates a new css::ImageValue to represent the url() information passed
- * to the constructor.  This ImageValue is held on to for the comparisons done
- * in DefinitelyEquals(), so that we don't need to call into the non-OMT-safe
- * Equals() on the nsIURI objects returned from imgRequestProxy::GetURI().
- */
-class nsStyleImageRequest
-{
-public:
-  // Flags describing whether the imgRequestProxy must be tracked in the
-  // ImageTracker, whether LockImage/UnlockImage calls will be made
-  // when obtaining and releasing the imgRequestProxy, and whether
-  // RequestDiscard will be called on release.
-  enum class Mode : uint8_t {
-    Track   = 0x1,  // used by all except nsCursorImage
-    Lock    = 0x2,  // used by all except nsStyleContentData
-    Discard = 0x4,  // used only by nsCursorImage
-  };
-
-  // Must be called from the main thread.
-  nsStyleImageRequest(Mode aModeFlags,
-                      imgRequestProxy* aRequestProxy,
-                      mozilla::css::ImageValue* aImageValue,
-                      mozilla::dom::ImageTracker* aImageTracker);
-
-  // Can be called from any thread, but Resolve() must be called later
-  // on the main thread before get() can be used.
-  nsStyleImageRequest(
-      Mode aModeFlags,
-      nsStringBuffer* aURLBuffer,
-      already_AddRefed<mozilla::PtrHolder<nsIURI>> aBaseURI,
-      already_AddRefed<mozilla::PtrHolder<nsIURI>> aReferrer,
-      already_AddRefed<mozilla::PtrHolder<nsIPrincipal>> aPrincipal);
-
-  bool Resolve(nsPresContext* aPresContext);
-  bool IsResolved() const { return mResolved; }
-
-  imgRequestProxy* get() {
-    MOZ_ASSERT(IsResolved(), "Resolve() must be called first");
-    MOZ_ASSERT(NS_IsMainThread());
-    return mRequestProxy.get();
-  }
-  const imgRequestProxy* get() const {
-    return const_cast<nsStyleImageRequest*>(this)->get();
-  }
-
-  // Returns whether the ImageValue objects in the two nsStyleImageRequests
-  // return true from URLValueData::DefinitelyEqualURIs.
-  bool DefinitelyEquals(const nsStyleImageRequest& aOther) const;
-
-  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(nsStyleImageRequest);
-
-private:
-  ~nsStyleImageRequest();
-  nsStyleImageRequest& operator=(const nsStyleImageRequest& aOther) = delete;
-
-  void MaybeTrackAndLock();
-
-  RefPtr<imgRequestProxy> mRequestProxy;
-  RefPtr<mozilla::css::ImageValue> mImageValue;
-  RefPtr<mozilla::dom::ImageTracker> mImageTracker;
-
-  Mode mModeFlags;
-  bool mResolved;
-};
-
-MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(nsStyleImageRequest::Mode)
-
 enum nsStyleImageType {
   eStyleImageType_Null,
   eStyleImageType_Image,
@@ -422,29 +325,23 @@ struct nsStyleImage
   nsStyleImage& operator=(const nsStyleImage& aOther);
 
   void SetNull();
-  void SetImageRequest(already_AddRefed<nsStyleImageRequest> aImage);
+  void SetImageData(imgRequestProxy* aImage);
+  void TrackImage(nsPresContext* aContext);
+  void UntrackImage(nsPresContext* aContext);
   void SetGradientData(nsStyleGradient* aGradient);
   void SetElementId(const char16_t* aElementId);
   void SetCropRect(mozilla::UniquePtr<nsStyleSides> aCropRect);
 
-  void ResolveImage(nsPresContext* aContext) {
-    MOZ_ASSERT(mType != eStyleImageType_Image || mImage);
-    if (mType == eStyleImageType_Image && !mImage->IsResolved()) {
-      mImage->Resolve(aContext);
-    }
-  }
-
   nsStyleImageType GetType() const {
     return mType;
   }
-  nsStyleImageRequest* GetImageRequest() const {
+  imgRequestProxy* GetImageData() const {
     MOZ_ASSERT(mType == eStyleImageType_Image, "Data is not an image!");
     MOZ_ASSERT(mImage);
+    MOZ_ASSERT(mImageTracked,
+               "Should be tracking any image we're going to use!");
     return mImage;
   }
-  imgRequestProxy* GetImageData() const {
-    return GetImageRequest()->get();
-  }
   nsStyleGradient* GetGradientData() const {
     NS_ASSERTION(mType == eStyleImageType_Gradient, "Data is not a gradient!");
     return mGradient;
@@ -537,13 +434,16 @@ private:
 
   nsStyleImageType mType;
   union {
-    nsStyleImageRequest* mImage;
+    imgRequestProxy* mImage;
     nsStyleGradient* mGradient;
     char16_t* mElementId;
   };
 
   // This is _currently_ used only in conjunction with eStyleImageType_Image.
   mozilla::UniquePtr<nsStyleSides> mCropRect;
+#ifdef DEBUG
+  bool mImageTracked;
+#endif
 };
 
 struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleColor
@@ -553,7 +453,6 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleColor
   ~nsStyleColor() {
     MOZ_COUNT_DTOR(nsStyleColor);
   }
-  void FinishStyle(nsPresContext* aPresContext) {}
 
   nscolor CalcComplexColor(const mozilla::StyleComplexColor& aColor) const {
     return mozilla::LinearBlendColors(aColor.mColor, mColor,
@@ -820,9 +719,16 @@ struct nsStyleImageLayers {
     // Initialize mRepeat and mOrigin by specified layer type
     void Initialize(LayerType aType);
 
-    void ResolveImage(nsPresContext* aContext) {
+    // Register/unregister images with the document. We do this only
+    // after the dust has settled in ComputeBackgroundData.
+    void TrackImages(nsPresContext* aContext) {
       if (mImage.GetType() == eStyleImageType_Image) {
-        mImage.ResolveImage(aContext);
+        mImage.TrackImage(aContext);
+      }
+    }
+    void UntrackImages(nsPresContext* aContext) {
+      if (mImage.GetType() == eStyleImageType_Image) {
+        mImage.UntrackImage(aContext);
       }
     }
 
@@ -872,11 +778,15 @@ struct nsStyleImageLayers {
 
   const Layer& BottomLayer() const { return mLayers[mImageCount - 1]; }
 
-  void ResolveImages(nsPresContext* aContext) {
+  void TrackImages(nsPresContext* aContext) {
     for (uint32_t i = 0; i < mImageCount; ++i) {
-      mLayers[i].ResolveImage(aContext);
+        mLayers[i].TrackImages(aContext);
     }
   }
+  void UntrackImages(nsPresContext* aContext) {
+    for (uint32_t i = 0; i < mImageCount; ++i)
+      mLayers[i].UntrackImages(aContext);
+  }
 
   nsChangeHint CalcDifference(const nsStyleImageLayers& aNewLayers,
                               nsStyleImageLayers::LayerType aType) const;
@@ -899,11 +809,6 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleBackground {
   nsStyleBackground(const nsStyleBackground& aOther);
   ~nsStyleBackground();
 
-  // Resolves and tracks the images in mImage.  Only called with a Servo-backed
-  // style system, where those images must be resolved later than the OMT
-  // nsStyleBackground constructor call.
-  void FinishStyle(nsPresContext* aPresContext);
-
   void* operator new(size_t sz, nsStyleBackground* aSelf) { return aSelf; }
   void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
@@ -955,7 +860,6 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleMargin
   ~nsStyleMargin() {
     MOZ_COUNT_DTOR(nsStyleMargin);
   }
-  void FinishStyle(nsPresContext* aPresContext) {}
 
   void* operator new(size_t sz, nsStyleMargin* aSelf) { return aSelf; }
   void* operator new(size_t sz, nsPresContext* aContext) {
@@ -1003,7 +907,6 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStylePadding
   ~nsStylePadding() {
     MOZ_COUNT_DTOR(nsStylePadding);
   }
-  void FinishStyle(nsPresContext* aPresContext) {}
 
   void* operator new(size_t sz, nsStylePadding* aSelf) { return aSelf; }
   void* operator new(size_t sz, nsPresContext* aContext) {
@@ -1212,11 +1115,6 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleBorder
   nsStyleBorder(const nsStyleBorder& aBorder);
   ~nsStyleBorder();
 
-  // Resolves and tracks mBorderImageSource.  Only called with a Servo-backed
-  // style system, where those images must be resolved later than the OMT
-  // nsStyleBorder constructor call.
-  void FinishStyle(nsPresContext* aPresContext);
-
   void* operator new(size_t sz, nsStyleBorder* aSelf) { return aSelf; }
   void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
@@ -1319,10 +1217,16 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleBorder
     return mBorderImageSource.IsLoaded();
   }
 
-  void ResolveImage(nsPresContext* aContext)
+  void TrackImage(nsPresContext* aContext)
   {
     if (mBorderImageSource.GetType() == eStyleImageType_Image) {
-      mBorderImageSource.ResolveImage(aContext);
+      mBorderImageSource.TrackImage(aContext);
+    }
+  }
+  void UntrackImage(nsPresContext* aContext)
+  {
+    if (mBorderImageSource.GetType() == eStyleImageType_Image) {
+      mBorderImageSource.UntrackImage(aContext);
     }
   }
 
@@ -1439,7 +1343,6 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleOutline
   ~nsStyleOutline() {
     MOZ_COUNT_DTOR(nsStyleOutline);
   }
-  void FinishStyle(nsPresContext* aPresContext) {}
 
   void* operator new(size_t sz, nsStyleOutline* aSelf) { return aSelf; }
   void* operator new(size_t sz, nsPresContext* aContext) {
@@ -1514,8 +1417,6 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleList
   nsStyleList(const nsStyleList& aStyleList);
   ~nsStyleList();
 
-  void FinishStyle(nsPresContext* aPresContext);
-
   void* operator new(size_t sz, nsStyleList* aSelf) { return aSelf; }
   void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
@@ -1545,9 +1446,16 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleList
     sNoneQuotes = nullptr;
   }
 
-  imgRequestProxy* GetListStyleImage() const
+  imgRequestProxy* GetListStyleImage() const { return mListStyleImage; }
+  void SetListStyleImage(imgRequestProxy* aReq)
   {
-    return mListStyleImage ? mListStyleImage->get() : nullptr;
+    if (mListStyleImage) {
+      mListStyleImage->UnlockImage();
+    }
+    mListStyleImage = aReq;
+    if (mListStyleImage) {
+      mListStyleImage->LockImage();
+    }
   }
 
   void GetListStyleType(nsSubstring& aType) const { mCounterStyle->GetStyleName(aType); }
@@ -1575,10 +1483,10 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleList
   void SetQuotesNone();
   void SetQuotes(nsStyleQuoteValues::QuotePairArray&& aValues);
 
-  uint8_t mListStylePosition;                  // [inherited]
-  RefPtr<nsStyleImageRequest> mListStyleImage; // [inherited]
+  uint8_t   mListStylePosition;         // [inherited]
 private:
   RefPtr<mozilla::CounterStyle> mCounterStyle; // [inherited]
+  RefPtr<imgRequestProxy> mListStyleImage; // [inherited]
   RefPtr<nsStyleQuoteValues> mQuotes;   // [inherited]
   nsStyleList& operator=(const nsStyleList& aOther) = delete;
 public:
@@ -1737,7 +1645,6 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStylePosition
   explicit nsStylePosition(StyleStructContext aContext);
   nsStylePosition(const nsStylePosition& aOther);
   ~nsStylePosition();
-  void FinishStyle(nsPresContext* aPresContext) {}
 
   void* operator new(size_t sz, nsStylePosition* aSelf) { return aSelf; }
   void* operator new(size_t sz, nsPresContext* aContext) {
@@ -1974,7 +1881,6 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleTextReset
   explicit nsStyleTextReset(StyleStructContext aContext);
   nsStyleTextReset(const nsStyleTextReset& aOther);
   ~nsStyleTextReset();
-  void FinishStyle(nsPresContext* aPresContext) {}
 
   void* operator new(size_t sz, nsStyleTextReset* aSelf) { return aSelf; }
   void* operator new(size_t sz, nsPresContext* aContext) {
@@ -2023,7 +1929,6 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleText
   explicit nsStyleText(StyleStructContext aContext);
   nsStyleText(const nsStyleText& aOther);
   ~nsStyleText();
-  void FinishStyle(nsPresContext* aPresContext) {}
 
   void* operator new(size_t sz, nsStyleText* aSelf) { return aSelf; }
   void* operator new(size_t sz, nsPresContext* aContext) {
@@ -2242,7 +2147,6 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleVisibility
   ~nsStyleVisibility() {
     MOZ_COUNT_DTOR(nsStyleVisibility);
   }
-  void FinishStyle(nsPresContext* aPresContext) {}
 
   void* operator new(size_t sz, nsStyleVisibility* aSelf) { return aSelf; }
   void* operator new(size_t sz, nsPresContext* aContext) {
@@ -2750,7 +2654,6 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleDisplay
   ~nsStyleDisplay() {
     MOZ_COUNT_DTOR(nsStyleDisplay);
   }
-  void FinishStyle(nsPresContext* aPresContext) {}
 
   void* operator new(size_t sz, nsStyleDisplay* aSelf) { return aSelf; }
   void* operator new(size_t sz, nsPresContext* aContext) {
@@ -3062,7 +2965,6 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleTable
   explicit nsStyleTable(StyleStructContext aContext);
   nsStyleTable(const nsStyleTable& aOther);
   ~nsStyleTable();
-  void FinishStyle(nsPresContext* aPresContext) {}
 
   void* operator new(size_t sz, nsStyleTable* aSelf) { return aSelf; }
   void* operator new(size_t sz, nsPresContext* aContext) {
@@ -3094,7 +2996,6 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleTableBorder
   explicit nsStyleTableBorder(StyleStructContext aContext);
   nsStyleTableBorder(const nsStyleTableBorder& aOther);
   ~nsStyleTableBorder();
-  void FinishStyle(nsPresContext* aPresContext) {}
 
   void* operator new(size_t sz, nsStyleTableBorder* aSelf) { return aSelf; }
   void* operator new(size_t sz, nsPresContext* aContext) {
@@ -3172,8 +3073,8 @@ struct nsStyleContentData
     return !(*this == aOther);
   }
 
-  void TrackImage(mozilla::dom::ImageTracker* aImageTracker);
-  void UntrackImage(mozilla::dom::ImageTracker* aImageTracker);
+  void TrackImage(nsPresContext* aContext);
+  void UntrackImage(nsPresContext* aContext);
 
   void SetImage(imgRequestProxy* aRequest)
   {
@@ -3203,7 +3104,6 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleContent
   explicit nsStyleContent(StyleStructContext aContext);
   nsStyleContent(const nsStyleContent& aContent);
   ~nsStyleContent();
-  void FinishStyle(nsPresContext* aPresContext) {}
 
   void* operator new(size_t sz, nsStyleContent* aSelf) { return aSelf; }
   void* operator new(size_t sz, nsPresContext* aContext) {
@@ -3286,7 +3186,6 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleUIReset
   explicit nsStyleUIReset(StyleStructContext aContext);
   nsStyleUIReset(const nsStyleUIReset& aOther);
   ~nsStyleUIReset();
-  void FinishStyle(nsPresContext* aPresContext) {}
 
   void* operator new(size_t sz, nsStyleUIReset* aSelf) { return aSelf; }
   void* operator new(size_t sz, nsPresContext* aContext) {
@@ -3359,7 +3258,6 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleUserInterface
   explicit nsStyleUserInterface(StyleStructContext aContext);
   nsStyleUserInterface(const nsStyleUserInterface& aOther);
   ~nsStyleUserInterface();
-  void FinishStyle(nsPresContext* aPresContext) {}
 
   void* operator new(size_t sz, nsStyleUserInterface* aSelf) { return aSelf; }
   void* operator new(size_t sz, nsPresContext* aContext) {
@@ -3403,7 +3301,6 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleXUL
   explicit nsStyleXUL(StyleStructContext aContext);
   nsStyleXUL(const nsStyleXUL& aSource);
   ~nsStyleXUL();
-  void FinishStyle(nsPresContext* aPresContext) {}
 
   void* operator new(size_t sz, nsStyleXUL* aSelf) { return aSelf; }
   void* operator new(size_t sz, nsPresContext* aContext) {
@@ -3443,7 +3340,6 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleColumn
   explicit nsStyleColumn(StyleStructContext aContext);
   nsStyleColumn(const nsStyleColumn& aSource);
   ~nsStyleColumn();
-  void FinishStyle(nsPresContext* aPresContext) {}
 
   void* operator new(size_t sz, nsStyleColumn* aSelf) { return aSelf; }
   void* operator new(size_t sz, nsPresContext* aContext) {
@@ -3568,7 +3464,6 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleSVG
   explicit nsStyleSVG(StyleStructContext aContext);
   nsStyleSVG(const nsStyleSVG& aSource);
   ~nsStyleSVG();
-  void FinishStyle(nsPresContext* aPresContext) {}
 
   void* operator new(size_t sz, nsStyleSVG* aSelf) { return aSelf; }
   void* operator new(size_t sz, nsPresContext* aContext) {
@@ -3702,7 +3597,6 @@ struct nsStyleFilter
   nsStyleFilter();
   nsStyleFilter(const nsStyleFilter& aSource);
   ~nsStyleFilter();
-  void FinishStyle(nsPresContext* aPresContext) {}
 
   nsStyleFilter& operator=(const nsStyleFilter& aOther);
 
@@ -3760,11 +3654,6 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleSVGReset
   nsStyleSVGReset(const nsStyleSVGReset& aSource);
   ~nsStyleSVGReset();
 
-  // Resolves and tracks the images in mMask.  Only called with a Servo-backed
-  // style system, where those images must be resolved later than the OMT
-  // nsStyleSVGReset constructor call.
-  void FinishStyle(nsPresContext* aPresContext);
-
   void* operator new(size_t sz, nsStyleSVGReset* aSelf) { return aSelf; }
   void* operator new(size_t sz, nsPresContext* aContext) {
     return aContext->PresShell()->
@@ -3816,7 +3705,6 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleVariables
   explicit nsStyleVariables(StyleStructContext aContext);
   nsStyleVariables(const nsStyleVariables& aSource);
   ~nsStyleVariables();
-  void FinishStyle(nsPresContext* aPresContext) {}
 
   void* operator new(size_t sz, nsStyleVariables* aSelf) { return aSelf; }
   void* operator new(size_t sz, nsPresContext* aContext) {
@@ -3847,7 +3735,6 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleEffects
   explicit nsStyleEffects(StyleStructContext aContext);
   nsStyleEffects(const nsStyleEffects& aSource);
   ~nsStyleEffects();
-  void FinishStyle(nsPresContext* aPresContext) {}
 
   void* operator new(size_t sz, nsStyleEffects* aSelf) { return aSelf; }
   void* operator new(size_t sz, nsPresContext* aContext) {