diff --git a/layout/style/FontFaceSet.cpp b/layout/style/FontFaceSet.cpp
index 5c0525f0bf53..93fbfe70ba7b 100644
--- a/layout/style/FontFaceSet.cpp
+++ b/layout/style/FontFaceSet.cpp
@@ -125,19 +125,14 @@ FontFaceSet::FontFaceSet(nsPIDOMWindow* aWindow, nsIDocument* aDocument)
   mUserFontSet = new UserFontSet(this);
 }
 
-static PLDHashOperator DestroyIterator(nsPtrHashKey<nsFontFaceLoader>* aKey,
-                                       void* aUserArg)
-{
-  aKey->GetKey()->Cancel();
-  return PL_DHASH_REMOVE;
-}
-
 FontFaceSet::~FontFaceSet()
 {
   MOZ_COUNT_DTOR(FontFaceSet);
 
   Disconnect();
-  mLoaders.EnumerateEntries(DestroyIterator, nullptr);
+  for (auto it = mLoaders.Iter(); !it.Done(); it.Next()) {
+    it.Get()->GetKey()->Cancel();
+  }
 }
 
 JSObject*
diff --git a/layout/style/ImageLoader.cpp b/layout/style/ImageLoader.cpp
index 9b5a3fe22b90..869f343b7848 100644
--- a/layout/style/ImageLoader.cpp
+++ b/layout/style/ImageLoader.cpp
@@ -45,22 +45,6 @@ ImageLoader::SetAnimationModeEnumerator(nsISupports* aKey, FrameSet* aValue,
   return PL_DHASH_NEXT;
 }
 
-static PLDHashOperator
-ClearImageHashSet(nsPtrHashKey<ImageLoader::Image>* aKey, void* aClosure)
-{
-  nsIDocument* doc = static_cast<nsIDocument*>(aClosure);
-  ImageLoader::Image* image = aKey->GetKey();
-
-  imgIRequest* request = image->mRequests.GetWeak(doc);
-  if (request) {
-    request->CancelAndForgetObserver(NS_BINDING_ABORTED);
-  }
-
-  image->mRequests.Remove(doc);
-
-  return PL_DHASH_REMOVE;
-}
-
 void
 ImageLoader::DropDocumentReference()
 {
@@ -68,7 +52,17 @@ ImageLoader::DropDocumentReference()
   // on the document being null) as that means the presshell has already
   // been destroyed, and it also calls ClearFrames when it is destroyed.
   ClearFrames(GetPresContext());
-  mImages.EnumerateEntries(&ClearImageHashSet, mDocument);
+
+  for (auto it = mImages.Iter(); !it.Done(); it.Next()) {
+    ImageLoader::Image* image = it.Get()->GetKey();
+    imgIRequest* request = image->mRequests.GetWeak(mDocument);
+    if (request) {
+      request->CancelAndForgetObserver(NS_BINDING_ABORTED);
+    }
+    image->mRequests.Remove(mDocument);
+  }
+  mImages.Clear();
+
   mDocument = nullptr;
 }
 
diff --git a/layout/svg/nsSVGEffects.cpp b/layout/svg/nsSVGEffects.cpp
index bec535ab66d3..d35f3c69e9d2 100644
--- a/layout/svg/nsSVGEffects.cpp
+++ b/layout/svg/nsSVGEffects.cpp
@@ -659,30 +659,6 @@ nsSVGEffects::GetFilterProperty(nsIFrame *aFrame)
     (aFrame->Properties().Get(FilterProperty()));
 }
 
-static PLDHashOperator
-GatherEnumerator(nsPtrHashKey<nsSVGRenderingObserver>* aEntry, void* aArg)
-{
-  nsTArray<nsSVGRenderingObserver*>* array =
-    static_cast<nsTArray<nsSVGRenderingObserver*>*>(aArg);
-  array->AppendElement(aEntry->GetKey());
-
-  return PL_DHASH_REMOVE;
-}
-
-static PLDHashOperator
-GatherEnumeratorForReflow(nsPtrHashKey<nsSVGRenderingObserver>* aEntry, void* aArg)
-{
-  if (!aEntry->GetKey()->ObservesReflow()) {
-    return PL_DHASH_NEXT;
-  }
-
-  nsTArray<nsSVGRenderingObserver*>* array =
-    static_cast<nsTArray<nsSVGRenderingObserver*>*>(aArg);
-  array->AppendElement(aEntry->GetKey());
-
-  return PL_DHASH_REMOVE;
-}
-
 void
 nsSVGRenderingObserverList::InvalidateAll()
 {
@@ -691,8 +667,10 @@ nsSVGRenderingObserverList::InvalidateAll()
 
   nsAutoTArray<nsSVGRenderingObserver*,10> observers;
 
-  // The PL_DHASH_REMOVE in GatherEnumerator drops all our observers here:
-  mObservers.EnumerateEntries(GatherEnumerator, &observers);
+  for (auto it = mObservers.Iter(); !it.Done(); it.Next()) {
+    observers.AppendElement(it.Get()->GetKey());
+  }
+  mObservers.Clear();
 
   for (uint32_t i = 0; i < observers.Length(); ++i) {
     observers[i]->InvalidateViaReferencedElement();
@@ -707,8 +685,13 @@ nsSVGRenderingObserverList::InvalidateAllForReflow()
 
   nsAutoTArray<nsSVGRenderingObserver*,10> observers;
 
-  // The PL_DHASH_REMOVE in GatherEnumerator drops all our observers here:
-  mObservers.EnumerateEntries(GatherEnumeratorForReflow, &observers);
+  for (auto it = mObservers.Iter(); !it.Done(); it.Next()) {
+    nsSVGRenderingObserver* obs = it.Get()->GetKey();
+    if (obs->ObservesReflow()) {
+      observers.AppendElement(obs);
+      it.Remove();
+    }
+  }
 
   for (uint32_t i = 0; i < observers.Length(); ++i) {
     observers[i]->InvalidateViaReferencedElement();
@@ -720,8 +703,10 @@ nsSVGRenderingObserverList::RemoveAll()
 {
   nsAutoTArray<nsSVGRenderingObserver*,10> observers;
 
-  // The PL_DHASH_REMOVE in GatherEnumerator drops all our observers here:
-  mObservers.EnumerateEntries(GatherEnumerator, &observers);
+  for (auto it = mObservers.Iter(); !it.Done(); it.Next()) {
+    observers.AppendElement(it.Get()->GetKey());
+  }
+  mObservers.Clear();
 
   // Our list is now cleared.  We need to notify the observers we've removed,
   // so they can update their state & remove themselves as mutation-observers.
diff --git a/layout/svg/nsSVGOuterSVGFrame.cpp b/layout/svg/nsSVGOuterSVGFrame.cpp
index de79d213608e..3d08d4b62584 100644
--- a/layout/svg/nsSVGOuterSVGFrame.cpp
+++ b/layout/svg/nsSVGOuterSVGFrame.cpp
@@ -623,19 +623,14 @@ nsDisplayOuterSVG::Paint(nsDisplayListBuilder* aBuilder,
 #endif
 }
 
-static PLDHashOperator CheckForeignObjectInvalidatedArea(nsPtrHashKey<nsSVGForeignObjectFrame>* aEntry, void* aData)
-{
-  nsRegion* region = static_cast<nsRegion*>(aData);
-  region->Or(*region, aEntry->GetKey()->GetInvalidRegion());
-  return PL_DHASH_NEXT;
-}
-
 nsRegion
 nsSVGOuterSVGFrame::FindInvalidatedForeignObjectFrameChildren(nsIFrame* aFrame)
 {
   nsRegion result;
   if (mForeignObjectHash && mForeignObjectHash->Count()) {
-    mForeignObjectHash->EnumerateEntries(CheckForeignObjectInvalidatedArea, &result);
+    for (auto it = mForeignObjectHash->Iter(); !it.Done(); it.Next()) {
+      result.Or(result, it.Get()->GetKey()->GetInvalidRegion());
+    }
   }
   return result;
 }