diff --git a/browser/base/content/browser-fullZoom.js b/browser/base/content/browser-fullZoom.js
index 4f22b6e92d6b..8c85a7167aeb 100644
--- a/browser/base/content/browser-fullZoom.js
+++ b/browser/base/content/browser-fullZoom.js
@@ -50,7 +50,6 @@ var FullZoom = {
   init: function FullZoom_init() {
     gBrowser.addEventListener("DoZoomEnlargeBy10", this);
     gBrowser.addEventListener("DoZoomReduceBy10", this);
-    window.addEventListener("MozScaleGestureComplete", this);
 
     // Register ourselves with the service so we know when our pref changes.
     this._cps2 = Cc["@mozilla.org/content-pref/service;1"].getService(
@@ -87,7 +86,6 @@ var FullZoom = {
     this._cps2.removeObserverForName(this.name, this);
     gBrowser.removeEventListener("DoZoomEnlargeBy10", this);
     gBrowser.removeEventListener("DoZoomReduceBy10", this);
-    window.removeEventListener("MozScaleGestureComplete", this);
   },
 
   // Event Handlers
@@ -102,11 +100,6 @@ var FullZoom = {
       case "DoZoomReduceBy10":
         this.changeZoomBy(this._getTargetedBrowser(event), -0.1);
         break;
-      case "MozScaleGestureComplete": {
-        let nonDefaultScalingZoom = event.detail != 1.0;
-        this.updateCommands(nonDefaultScalingZoom);
-        break;
-      }
     }
   },
 
@@ -330,18 +323,7 @@ var FullZoom = {
 
   // update state of zoom menu items
 
-  /**
-   * Updates the current windows Zoom commands for zooming in, zooming out
-   * and resetting the zoom level. Dispatches a ZoomCommandsUpdated event on
-   * the window when the commands have been updated.
-   *
-   * @param {boolean} [forceResetEnabled=false]
-   *   Set to true if the zoom reset command should be enabled regardless of
-   *   whether or not the ZoomManager.zoom level is at 1.0. This is specifically
-   *   for when using scaling zoom via the pinch gesture which doesn't cause
-   *   the ZoomManager.zoom level to change.
-   */
-  updateCommands: function FullZoom_updateCommands(forceResetEnabled = false) {
+  updateCommands: function FullZoom_updateCommands() {
     let zoomLevel = ZoomManager.zoom;
     let reduceCmd = document.getElementById("cmd_fullZoomReduce");
     if (zoomLevel == ZoomManager.MIN) {
@@ -358,7 +340,7 @@ var FullZoom = {
     }
 
     let resetCmd = document.getElementById("cmd_fullZoomReset");
-    if (zoomLevel == 1 && !forceResetEnabled) {
+    if (zoomLevel == 1) {
       resetCmd.setAttribute("disabled", "true");
     } else {
       resetCmd.removeAttribute("disabled");
diff --git a/gfx/layers/apz/public/GeckoContentController.h b/gfx/layers/apz/public/GeckoContentController.h
index 69c6da8945c5..36d751b1c20a 100644
--- a/gfx/layers/apz/public/GeckoContentController.h
+++ b/gfx/layers/apz/public/GeckoContentController.h
@@ -147,9 +147,6 @@ class GeckoContentController {
 
   virtual void CancelAutoscroll(const ScrollableLayerGuid& aGuid) = 0;
 
-  virtual void NotifyScaleGestureComplete(const ScrollableLayerGuid& aGuid,
-                                          float aScale) = 0;
-
   virtual void UpdateOverscrollVelocity(const ScrollableLayerGuid& aGuid,
                                         float aX, float aY,
                                         bool aIsRootContent) {}
diff --git a/gfx/layers/apz/src/AsyncPanZoomController.cpp b/gfx/layers/apz/src/AsyncPanZoomController.cpp
index 47edc252f636..bdf5d1219aeb 100644
--- a/gfx/layers/apz/src/AsyncPanZoomController.cpp
+++ b/gfx/layers/apz/src/AsyncPanZoomController.cpp
@@ -738,7 +738,6 @@ AsyncPanZoomController::AsyncPanZoomController(
                            kViewportMaxScale / ParentLayerToScreenScale(1)),
       mLastSampleTime(GetFrameTime()),
       mLastCheckerboardReport(GetFrameTime()),
-      mLastNotifiedZoom(),
       mOverscrollEffect(MakeUnique<OverscrollEffect>(*this)),
       mState(NOTHING),
       mX(this),
@@ -4387,14 +4386,6 @@ void AsyncPanZoomController::RequestContentRepaint(
   RepaintRequest request(aFrameMetrics, aDisplayportMargins, aUpdateType,
                          animationType, mScrollGeneration);
 
-  if (request.IsRootContent() && request.GetZoom() != mLastNotifiedZoom &&
-      mState != PINCHING && mState != ANIMATING_ZOOM) {
-    controller->NotifyScaleGestureComplete(
-        GetGuid(),
-        (request.GetZoom() / request.GetDevPixelsPerCSSPixel()).scale);
-    mLastNotifiedZoom = request.GetZoom();
-  }
-
   // If we're trying to paint what we already think is painted, discard this
   // request since it's a pointless paint.
   if (request.GetDisplayPortMargins().WithinEpsilonOf(
diff --git a/gfx/layers/apz/src/AsyncPanZoomController.h b/gfx/layers/apz/src/AsyncPanZoomController.h
index 8f4078e651cf..7c297a14e450 100644
--- a/gfx/layers/apz/src/AsyncPanZoomController.h
+++ b/gfx/layers/apz/src/AsyncPanZoomController.h
@@ -1081,10 +1081,6 @@ class AsyncPanZoomController {
   // to allow panning by moving multiple fingers (thus moving the focus point).
   ParentLayerPoint mLastZoomFocus;
 
-  // Stores the previous zoom level at which we last sent a ScaleGestureComplete
-  // notification.
-  CSSToParentLayerScale mLastNotifiedZoom;
-
   RefPtr<AsyncPanZoomAnimation> mAnimation;
 
   UniquePtr<OverscrollEffectBase> mOverscrollEffect;
diff --git a/gfx/layers/apz/test/gtest/APZTestCommon.h b/gfx/layers/apz/test/gtest/APZTestCommon.h
index b5b4c1f92c7c..2419eff68d0f 100644
--- a/gfx/layers/apz/test/gtest/APZTestCommon.h
+++ b/gfx/layers/apz/test/gtest/APZTestCommon.h
@@ -154,8 +154,6 @@ class MockContentController : public GeckoContentController {
   MOCK_METHOD1(NotifyAsyncAutoscrollRejected,
                void(const ScrollableLayerGuid::ViewID&));
   MOCK_METHOD1(CancelAutoscroll, void(const ScrollableLayerGuid&));
-  MOCK_METHOD2(NotifyScaleGestureComplete,
-               void(const ScrollableLayerGuid&, float aScale));
 };
 
 class MockContentControllerDelayed : public MockContentController {
diff --git a/gfx/layers/apz/util/APZCCallbackHelper.cpp b/gfx/layers/apz/util/APZCCallbackHelper.cpp
index 79a41fc5d582..ff8bcd27d164 100644
--- a/gfx/layers/apz/util/APZCCallbackHelper.cpp
+++ b/gfx/layers/apz/util/APZCCallbackHelper.cpp
@@ -8,13 +8,10 @@
 
 #include "gfxPlatform.h"  // For gfxPlatform::UseTiling
 
-#include "mozilla/AsyncEventDispatcher.h"
 #include "mozilla/EventForwards.h"
-#include "mozilla/dom/CustomEvent.h"
 #include "mozilla/dom/Element.h"
 #include "mozilla/dom/MouseEventBinding.h"
 #include "mozilla/dom/BrowserParent.h"
-#include "mozilla/dom/ScriptSettings.h"
 #include "mozilla/IntegerPrintfMacros.h"
 #include "mozilla/layers/RepaintRequest.h"
 #include "mozilla/layers/WebRenderLayerManager.h"
@@ -32,7 +29,6 @@
 #include "nsIScrollableFrame.h"
 #include "nsLayoutUtils.h"
 #include "nsPrintfCString.h"
-#include "nsPIDOMWindow.h"
 #include "nsRefreshDriver.h"
 #include "nsString.h"
 #include "nsView.h"
@@ -873,38 +869,6 @@ void APZCCallbackHelper::CancelAutoscroll(
                                    data.get());
 }
 
-/* static */
-void APZCCallbackHelper::NotifyScaleGestureComplete(
-    const nsCOMPtr<nsIWidget>& aWidget, float aScale) {
-  MOZ_ASSERT(NS_IsMainThread());
-
-  if (nsView* view = nsView::GetViewFor(aWidget)) {
-    if (PresShell* presShell = view->GetPresShell()) {
-      dom::Document* doc = presShell->GetDocument();
-      MOZ_ASSERT(doc);
-      if (nsPIDOMWindowInner* win = doc->GetInnerWindow()) {
-        dom::AutoJSAPI jsapi;
-        if (!jsapi.Init(win)) {
-          return;
-        }
-
-        JSContext* cx = jsapi.cx();
-        JS::Rooted<JS::Value> detail(cx, JS::Float32Value(aScale));
-        RefPtr<dom::CustomEvent> event =
-            NS_NewDOMCustomEvent(doc, nullptr, nullptr);
-        event->InitCustomEvent(cx, u"MozScaleGestureComplete"_ns,
-                               /* CanBubble */ true,
-                               /* Cancelable */ false, detail);
-        event->SetTrusted(true);
-        AsyncEventDispatcher* dispatcher = new AsyncEventDispatcher(doc, event);
-        dispatcher->mOnlyChromeDispatch = ChromeOnlyDispatch::eYes;
-
-        dispatcher->PostDOMEvent();
-      }
-    }
-  }
-}
-
 /* static */
 void APZCCallbackHelper::NotifyPinchGesture(
     PinchGestureInput::PinchGestureType aType,
diff --git a/gfx/layers/apz/util/APZCCallbackHelper.h b/gfx/layers/apz/util/APZCCallbackHelper.h
index 2048bdde1502..89e3e0787ccc 100644
--- a/gfx/layers/apz/util/APZCCallbackHelper.h
+++ b/gfx/layers/apz/util/APZCCallbackHelper.h
@@ -162,8 +162,6 @@ class APZCCallbackHelper {
       const ScrollableLayerGuid::ViewID& aScrollId);
 
   static void CancelAutoscroll(const ScrollableLayerGuid::ViewID& aScrollId);
-  static void NotifyScaleGestureComplete(const nsCOMPtr<nsIWidget>& aWidget,
-                                         float aScale);
 
   /*
    * Check if the scrollable frame is currently in the middle of a main thread
diff --git a/gfx/layers/apz/util/ChromeProcessController.cpp b/gfx/layers/apz/util/ChromeProcessController.cpp
index b594c5b7643c..e95e78e4fdb2 100644
--- a/gfx/layers/apz/util/ChromeProcessController.cpp
+++ b/gfx/layers/apz/util/ChromeProcessController.cpp
@@ -330,23 +330,3 @@ void ChromeProcessController::CancelAutoscroll(
 
   APZCCallbackHelper::CancelAutoscroll(aGuid.mScrollId);
 }
-
-void ChromeProcessController::NotifyScaleGestureComplete(
-    const ScrollableLayerGuid& aGuid, float aScale) {
-  if (!mUIThread->IsOnCurrentThread()) {
-    mUIThread->Dispatch(NewRunnableMethod<ScrollableLayerGuid, float>(
-        "layers::ChromeProcessController::NotifyScaleGestureComplete", this,
-        &ChromeProcessController::NotifyScaleGestureComplete, aGuid, aScale));
-    return;
-  }
-
-  if (mWidget) {
-    // Dispatch the call to APZCCallbackHelper::NotifyScaleGestureComplete
-    // to the main thread so that it runs asynchronously from the current call.
-    // This is because the call can run arbitrary JS code, which can also spin
-    // the event loop and cause undesirable re-entrancy in APZ.
-    mUIThread->Dispatch(NewRunnableFunction(
-        "layers::ChromeProcessController::NotifyScaleGestureComplete",
-        &APZCCallbackHelper::NotifyScaleGestureComplete, mWidget, aScale));
-  }
-}
diff --git a/gfx/layers/apz/util/ChromeProcessController.h b/gfx/layers/apz/util/ChromeProcessController.h
index 3239762129d9..2a0a3051fda6 100644
--- a/gfx/layers/apz/util/ChromeProcessController.h
+++ b/gfx/layers/apz/util/ChromeProcessController.h
@@ -75,8 +75,6 @@ class ChromeProcessController : public mozilla::layers::GeckoContentController {
   void NotifyAsyncAutoscrollRejected(
       const ScrollableLayerGuid::ViewID& aScrollId) override;
   void CancelAutoscroll(const ScrollableLayerGuid& aGuid) override;
-  void NotifyScaleGestureComplete(const ScrollableLayerGuid& aGuid,
-                                  float aScale) override;
 
   PresShell* GetTopLevelPresShell() const override { return GetPresShell(); }
 
diff --git a/gfx/layers/apz/util/ContentProcessController.cpp b/gfx/layers/apz/util/ContentProcessController.cpp
index 40bbe72be37c..0c9071d30938 100644
--- a/gfx/layers/apz/util/ContentProcessController.cpp
+++ b/gfx/layers/apz/util/ContentProcessController.cpp
@@ -97,12 +97,6 @@ void ContentProcessController::CancelAutoscroll(
   MOZ_ASSERT_UNREACHABLE("Unexpected message to content process");
 }
 
-void ContentProcessController::NotifyScaleGestureComplete(
-    const ScrollableLayerGuid& aGuid, float aScale) {
-  // This should never get called
-  MOZ_ASSERT_UNREACHABLE("Unexpected message to content process");
-}
-
 bool ContentProcessController::IsRepaintThread() { return NS_IsMainThread(); }
 
 void ContentProcessController::DispatchToRepaintThread(
diff --git a/gfx/layers/apz/util/ContentProcessController.h b/gfx/layers/apz/util/ContentProcessController.h
index 94b3208deb6b..f91ea9a27978 100644
--- a/gfx/layers/apz/util/ContentProcessController.h
+++ b/gfx/layers/apz/util/ContentProcessController.h
@@ -72,9 +72,6 @@ class ContentProcessController final : public GeckoContentController {
 
   void CancelAutoscroll(const ScrollableLayerGuid& aGuid) override;
 
-  void NotifyScaleGestureComplete(const ScrollableLayerGuid& aGuid,
-                                  float aScale) override;
-
   bool IsRepaintThread() override;
 
   void DispatchToRepaintThread(already_AddRefed<Runnable> aTask) override;
diff --git a/gfx/layers/ipc/APZCTreeManagerChild.cpp b/gfx/layers/ipc/APZCTreeManagerChild.cpp
index 7d0d31e595c1..d87a8c67943a 100644
--- a/gfx/layers/ipc/APZCTreeManagerChild.cpp
+++ b/gfx/layers/ipc/APZCTreeManagerChild.cpp
@@ -201,19 +201,5 @@ mozilla::ipc::IPCResult APZCTreeManagerChild::RecvCancelAutoscroll(
   return IPC_OK();
 }
 
-mozilla::ipc::IPCResult APZCTreeManagerChild::RecvNotifyScaleGestureComplete(
-    const ScrollableLayerGuid::ViewID& aScrollId, float aScale) {
-  // This will only get sent from the GPU process to the parent process, so
-  // this function should never get called in the content process.
-  MOZ_ASSERT(XRE_IsParentProcess());
-  MOZ_ASSERT(NS_IsMainThread());
-
-  if (mCompositorSession && mCompositorSession->GetWidget()) {
-    APZCCallbackHelper::NotifyScaleGestureComplete(
-        mCompositorSession->GetWidget(), aScale);
-  }
-  return IPC_OK();
-}
-
 }  // namespace layers
 }  // namespace mozilla
diff --git a/gfx/layers/ipc/APZCTreeManagerChild.h b/gfx/layers/ipc/APZCTreeManagerChild.h
index 3266b6bbce0e..7d38fd23ba86 100644
--- a/gfx/layers/ipc/APZCTreeManagerChild.h
+++ b/gfx/layers/ipc/APZCTreeManagerChild.h
@@ -85,9 +85,6 @@ class APZCTreeManagerChild : public IAPZCTreeManager,
   mozilla::ipc::IPCResult RecvCancelAutoscroll(
       const ScrollableLayerGuid::ViewID& aScrollId);
 
-  mozilla::ipc::IPCResult RecvNotifyScaleGestureComplete(
-      const ScrollableLayerGuid::ViewID& aScrollId, float aScale);
-
   virtual ~APZCTreeManagerChild();
 
  private:
diff --git a/gfx/layers/ipc/PAPZCTreeManager.ipdl b/gfx/layers/ipc/PAPZCTreeManager.ipdl
index b730513aba9b..ff2c510ff665 100644
--- a/gfx/layers/ipc/PAPZCTreeManager.ipdl
+++ b/gfx/layers/ipc/PAPZCTreeManager.ipdl
@@ -83,8 +83,6 @@ child:
                            Modifiers aModifiers);
 
   async CancelAutoscroll(ViewID aScrollId);
-
-  async NotifyScaleGestureComplete(ViewID aScrollId, float aScale);
 };
 
 } // namespace gfx
diff --git a/gfx/layers/ipc/RemoteContentController.cpp b/gfx/layers/ipc/RemoteContentController.cpp
index b419be6e4c86..8b110f13971d 100644
--- a/gfx/layers/ipc/RemoteContentController.cpp
+++ b/gfx/layers/ipc/RemoteContentController.cpp
@@ -399,56 +399,6 @@ void RemoteContentController::CancelAutoscrollCrossProcess(
   }
 }
 
-void RemoteContentController::NotifyScaleGestureComplete(
-    const ScrollableLayerGuid& aGuid, float aScale) {
-  if (XRE_GetProcessType() == GeckoProcessType_GPU) {
-    NotifyScaleGestureCompleteCrossProcess(aGuid, aScale);
-  } else {
-    NotifyScaleGestureCompleteInProcess(aGuid, aScale);
-  }
-}
-
-void RemoteContentController::NotifyScaleGestureCompleteInProcess(
-    const ScrollableLayerGuid& aGuid, float aScale) {
-  MOZ_ASSERT(XRE_IsParentProcess());
-
-  if (!NS_IsMainThread()) {
-    NS_DispatchToMainThread(NewRunnableMethod<ScrollableLayerGuid, float>(
-        "layers::RemoteContentController::NotifyScaleGestureCompleteInProcess",
-        this, &RemoteContentController::NotifyScaleGestureCompleteInProcess,
-        aGuid, aScale));
-    return;
-  }
-
-  RefPtr<GeckoContentController> rootController =
-      CompositorBridgeParent::GetGeckoContentControllerForRoot(aGuid.mLayersId);
-  if (rootController) {
-    rootController->NotifyScaleGestureComplete(aGuid, aScale);
-  }
-}
-
-void RemoteContentController::NotifyScaleGestureCompleteCrossProcess(
-    const ScrollableLayerGuid& aGuid, float aScale) {
-  MOZ_ASSERT(XRE_IsGPUProcess());
-
-  if (!mCompositorThread->IsOnCurrentThread()) {
-    mCompositorThread->Dispatch(NewRunnableMethod<ScrollableLayerGuid, float>(
-        "layers::RemoteContentController::"
-        "NotifyScaleGestureCompleteCrossProcess",
-        this, &RemoteContentController::NotifyScaleGestureCompleteCrossProcess,
-        aGuid, aScale));
-    return;
-  }
-
-  // The raw pointer to APZCTreeManagerParent is ok here because we are on the
-  // compositor thread.
-  if (APZCTreeManagerParent* parent =
-          CompositorBridgeParent::GetApzcTreeManagerParentForRoot(
-              aGuid.mLayersId)) {
-    Unused << parent->SendNotifyScaleGestureComplete(aGuid.mScrollId, aScale);
-  }
-}
-
 void RemoteContentController::ActorDestroy(ActorDestroyReason aWhy) {
   // This controller could possibly be kept alive longer after this
   // by a RefPtr, but it is no longer valid to send messages.
diff --git a/gfx/layers/ipc/RemoteContentController.h b/gfx/layers/ipc/RemoteContentController.h
index c8f74365991a..1f18323a3cad 100644
--- a/gfx/layers/ipc/RemoteContentController.h
+++ b/gfx/layers/ipc/RemoteContentController.h
@@ -81,9 +81,6 @@ class RemoteContentController : public GeckoContentController,
 
   void CancelAutoscroll(const ScrollableLayerGuid& aScrollId) override;
 
-  void NotifyScaleGestureComplete(const ScrollableLayerGuid& aGuid,
-                                  float aScale) override;
-
   void ActorDestroy(ActorDestroyReason aWhy) override;
 
   void Destroy() override;
@@ -109,10 +106,6 @@ class RemoteContentController : public GeckoContentController,
 
   void CancelAutoscrollInProcess(const ScrollableLayerGuid& aScrollId);
   void CancelAutoscrollCrossProcess(const ScrollableLayerGuid& aScrollId);
-  void NotifyScaleGestureCompleteInProcess(const ScrollableLayerGuid& aGuid,
-                                           float aScale);
-  void NotifyScaleGestureCompleteCrossProcess(const ScrollableLayerGuid& aGuid,
-                                              float aScale);
 };
 
 }  // namespace layers