--- a/gfx/layers/apz/public/GeckoContentController.h
+++ b/gfx/layers/apz/public/GeckoContentController.h
@@ -32,24 +32,16 @@ public:
   /**
    * Requests a paint of the given FrameMetrics |aFrameMetrics| from Gecko.
    * Implementations per-platform are responsible for actually handling this.
    * This method will always be called on the Gecko main thread.
    */
   virtual void RequestContentRepaint(const FrameMetrics& aFrameMetrics) = 0;
 
   /**
-   * Requests handling of a scroll snapping at the end of a fling gesture for
-   * the scrollable frame with the given scroll id. aDestination specifies the
-   * expected landing position of the fling if no snapping were to be performed.
-   */
-  virtual void RequestFlingSnap(const FrameMetrics::ViewID& aScrollId,
-                                const mozilla::CSSPoint& aDestination) = 0;
-
-  /**
    * Acknowledges the recipt of a scroll offset update for the scrollable
    * frame with the given scroll id. This is used to maintain consistency
    * between APZ and other sources of scroll changes.
    */
   virtual void AcknowledgeScrollUpdate(const FrameMetrics::ViewID& aScrollId,
                                        const uint32_t& aScrollGeneration) = 0;
 
   /**

--- a/gfx/layers/apz/util/APZCCallbackHelper.cpp
+++ b/gfx/layers/apz/util/APZCCallbackHelper.cpp
@@ -326,56 +326,16 @@ APZCCallbackHelper::InitializeRootDispla
     // nsRootBoxFrame::BuildDisplayList.
     nsLayoutUtils::SetDisplayPortMargins(content, aPresShell, ScreenMargin(), 0,
         nsLayoutUtils::RepaintMode::DoNotRepaint);
     nsLayoutUtils::SetZeroMarginDisplayPortOnAsyncScrollableAncestors(
         content->GetPrimaryFrame(), nsLayoutUtils::RepaintMode::DoNotRepaint);
   }
 }
 
-class FlingSnapEvent : public nsRunnable
-{
-    typedef mozilla::layers::FrameMetrics::ViewID ViewID;
-
-public:
-    FlingSnapEvent(const ViewID& aScrollId,
-                   const mozilla::CSSPoint& aDestination)
-        : mScrollId(aScrollId)
-        , mDestination(aDestination)
-    {
-    }
-
-    NS_IMETHOD Run() {
-        MOZ_ASSERT(NS_IsMainThread());
-
-        nsIScrollableFrame* sf = nsLayoutUtils::FindScrollableFrameFor(mScrollId);
-        if (sf) {
-            sf->FlingSnap(mDestination);
-        }
-
-        return NS_OK;
-    }
-
-protected:
-    ViewID mScrollId;
-    mozilla::CSSPoint mDestination;
-};
-
-void
-APZCCallbackHelper::RequestFlingSnap(const FrameMetrics::ViewID& aScrollId,
-                                     const mozilla::CSSPoint& aDestination)
-{
-    nsCOMPtr<nsIRunnable> r1 = new FlingSnapEvent(aScrollId, aDestination);
-    if (!NS_IsMainThread()) {
-        NS_DispatchToMainThread(r1);
-    } else {
-        r1->Run();
-    }
-}
-
 class AcknowledgeScrollUpdateEvent : public nsRunnable
 {
     typedef mozilla::layers::FrameMetrics::ViewID ViewID;
 
 public:
     AcknowledgeScrollUpdateEvent(const ViewID& aScrollId, const uint32_t& aScrollGeneration)
         : mScrollId(aScrollId)
         , mScrollGeneration(aScrollGeneration)

--- a/gfx/layers/apz/util/APZCCallbackHelper.h
+++ b/gfx/layers/apz/util/APZCCallbackHelper.h
@@ -61,24 +61,16 @@ public:
     static bool GetOrCreateScrollIdentifiers(nsIContent* aContent,
                                              uint32_t* aPresShellIdOut,
                                              FrameMetrics::ViewID* aViewIdOut);
 
     /* Initialize a zero-margin displayport on the root document element of the
        given presShell. */
     static void InitializeRootDisplayport(nsIPresShell* aPresShell);
 
-    /* Tell layout to perform scroll snapping for the scrollable frame with the
-     * given scroll id. aDestination specifies the expected landing position of
-     * a current fling or scrolling animation that should be used to select
-     * the scroll snap point.
-     */
-    static void RequestFlingSnap(const FrameMetrics::ViewID& aScrollId,
-                                 const mozilla::CSSPoint& aDestination);
-
     /* Tell layout that we received the scroll offset update for the given view ID, so
        that it accepts future scroll offset updates from APZ. */
     static void AcknowledgeScrollUpdate(const FrameMetrics::ViewID& aScrollId,
                                         const uint32_t& aScrollGeneration);
 
     /* Get the pres shell associated with the root content document enclosing |aContent|. */
     static nsIPresShell* GetRootContentDocumentPresShellForContent(nsIContent* aContent);
 

--- a/gfx/layers/apz/util/ChromeProcessController.cpp
+++ b/gfx/layers/apz/util/ChromeProcessController.cpp
@@ -64,23 +64,16 @@ ChromeProcessController::RequestContentR
 
 void
 ChromeProcessController::PostDelayedTask(Task* aTask, int aDelayMs)
 {
   MessageLoop::current()->PostDelayedTask(FROM_HERE, aTask, aDelayMs);
 }
 
 void
-ChromeProcessController::RequestFlingSnap(const FrameMetrics::ViewID& aScrollId,
-                                          const mozilla::CSSPoint& aDestination)
-{
-  APZCCallbackHelper::RequestFlingSnap(aScrollId, aDestination);
-}
-
-void
 ChromeProcessController::AcknowledgeScrollUpdate(const FrameMetrics::ViewID& aScrollId,
                                                  const uint32_t& aScrollGeneration)
 {
   APZCCallbackHelper::AcknowledgeScrollUpdate(aScrollId, aScrollGeneration);
 }
 
 void
 ChromeProcessController::Destroy()

--- a/gfx/layers/apz/util/ChromeProcessController.h
+++ b/gfx/layers/apz/util/ChromeProcessController.h
@@ -35,18 +35,16 @@ protected:
 public:
   explicit ChromeProcessController(nsIWidget* aWidget, APZEventState* aAPZEventState, APZCTreeManager* aAPZCTreeManager);
   ~ChromeProcessController();
   virtual void Destroy() override;
 
   // GeckoContentController interface
   virtual void RequestContentRepaint(const FrameMetrics& aFrameMetrics) override;
   virtual void PostDelayedTask(Task* aTask, int aDelayMs) override;
-  virtual void RequestFlingSnap(const FrameMetrics::ViewID& aScrollId,
-                                const mozilla::CSSPoint& aDestination) override;
   virtual void AcknowledgeScrollUpdate(const FrameMetrics::ViewID& aScrollId,
                                        const uint32_t& aScrollGeneration) override;
 
   virtual void HandleDoubleTap(const mozilla::CSSPoint& aPoint, Modifiers aModifiers,
                                const ScrollableLayerGuid& aGuid) override;
   virtual void HandleSingleTap(const mozilla::CSSPoint& aPoint, Modifiers aModifiers,
                                const ScrollableLayerGuid& aGuid) override;
   virtual void HandleLongTap(const mozilla::CSSPoint& aPoint, Modifiers aModifiers,

--- a/gfx/layers/ipc/APZChild.cpp
+++ b/gfx/layers/ipc/APZChild.cpp
@@ -90,24 +90,16 @@ APZChild::~APZChild()
 
 bool
 APZChild::RecvUpdateFrame(const FrameMetrics& aFrameMetrics)
 {
   return mBrowser->UpdateFrame(aFrameMetrics);
 }
 
 bool
-APZChild::RecvRequestFlingSnap(const FrameMetrics::ViewID& aScrollId,
-                               const mozilla::CSSPoint& aDestination)
-{
-  APZCCallbackHelper::RequestFlingSnap(aScrollId, aDestination);
-  return true;
-}
-
-bool
 APZChild::RecvAcknowledgeScrollUpdate(const ViewID& aScrollId,
                                       const uint32_t& aScrollGeneration)
 {
   APZCCallbackHelper::AcknowledgeScrollUpdate(aScrollId, aScrollGeneration);
   return true;
 }
 
 bool

--- a/gfx/layers/ipc/APZChild.h
+++ b/gfx/layers/ipc/APZChild.h
@@ -23,19 +23,16 @@ class APZChild final : public PAPZChild
 {
 public:
   static APZChild* Create(const dom::TabId& aTabId);
 
   ~APZChild();
 
   virtual bool RecvUpdateFrame(const FrameMetrics& frame) override;
 
-  virtual bool RecvRequestFlingSnap(const ViewID& aScrollID,
-                                    const CSSPoint& aDestination) override;
-
   virtual bool RecvAcknowledgeScrollUpdate(const ViewID& aScrollId,
                                            const uint32_t& aScrollGeneration) override;
 
   virtual bool RecvHandleDoubleTap(const CSSPoint& aPoint,
                                    const Modifiers& aModifiers,
                                    const ScrollableLayerGuid& aGuid) override;
 
   virtual bool RecvHandleSingleTap(const CSSPoint& aPoint,

--- a/gfx/layers/ipc/PAPZ.ipdl
+++ b/gfx/layers/ipc/PAPZ.ipdl
@@ -84,17 +84,16 @@ parent:
                               MaybeZoomConstraints aConstraints);
 
 child:
   async UpdateFrame(FrameMetrics frame);
 
   // The following methods correspond to functions on the GeckoContentController
   // interface in gfx/layers/apz/public/GeckoContentController.h. Refer to documentation
   // in that file for these functions.
-  async RequestFlingSnap(ViewID aScrollID, CSSPoint aDestination);
   async AcknowledgeScrollUpdate(ViewID aScrollId, uint32_t aScrollGeneration);
   async HandleDoubleTap(CSSPoint aPoint, Modifiers aModifiers, ScrollableLayerGuid aGuid);
   async HandleSingleTap(CSSPoint aPoint, Modifiers aModifiers, ScrollableLayerGuid aGuid, bool aCallTakeFocusForClickFromTap);
   async HandleLongTap(CSSPoint point, Modifiers aModifiers, ScrollableLayerGuid aGuid, uint64_t aInputBlockId);
   async NotifyAPZStateChange(ViewID aViewId, APZStateChange aChange, int aArg);
   async NotifyFlushComplete();
 
   async __delete__();

--- a/gfx/layers/ipc/RemoteContentController.cpp
+++ b/gfx/layers/ipc/RemoteContentController.cpp
@@ -47,34 +47,16 @@ RemoteContentController::RequestContentR
 {
   MOZ_ASSERT(NS_IsMainThread());
   if (CanSend()) {
     Unused << SendUpdateFrame(aFrameMetrics);
   }
 }
 
 void
-RemoteContentController::RequestFlingSnap(const FrameMetrics::ViewID& aScrollId,
-                                          const mozilla::CSSPoint& aDestination)
-{
-  if (MessageLoop::current() != mUILoop) {
-    // We have to send this message from the "UI thread" (main
-    // thread).
-    mUILoop->PostTask(
-      FROM_HERE,
-      NewRunnableMethod(this, &RemoteContentController::RequestFlingSnap,
-                        aScrollId, aDestination));
-    return;
-  }
-  if (CanSend()) {
-    Unused << SendRequestFlingSnap(aScrollId, aDestination);
-  }
-}
-
-void
 RemoteContentController::AcknowledgeScrollUpdate(const FrameMetrics::ViewID& aScrollId,
                                                  const uint32_t& aScrollGeneration)
 {
   if (MessageLoop::current() != mUILoop) {
     // We have to send this message from the "UI thread" (main
     // thread).
     mUILoop->PostTask(
       FROM_HERE,

--- a/gfx/layers/ipc/RemoteContentController.h
+++ b/gfx/layers/ipc/RemoteContentController.h
@@ -37,19 +37,16 @@ public:
   explicit RemoteContentController(uint64_t aLayersId,
                                    dom::TabParent* aBrowserParent);
 
   virtual ~RemoteContentController();
 
   // Needs to be called on the main thread.
   virtual void RequestContentRepaint(const FrameMetrics& aFrameMetrics) override;
 
-  virtual void RequestFlingSnap(const FrameMetrics::ViewID& aScrollId,
-                                const mozilla::CSSPoint& aDestination) override;
-
   virtual void AcknowledgeScrollUpdate(const FrameMetrics::ViewID& aScrollId,
                                        const uint32_t& aScrollGeneration) override;
 
   virtual void HandleDoubleTap(const CSSPoint& aPoint,
                                Modifiers aModifiers,
                                const ScrollableLayerGuid& aGuid) override;
 
   virtual void HandleSingleTap(const CSSPoint& aPoint,

--- a/layout/generic/nsGfxScrollFrame.cpp
+++ b/layout/generic/nsGfxScrollFrame.cpp
@@ -3911,22 +3911,16 @@ ScrollFrameHelper::ScrollSnap(nsIScrolla
                                     velocity.y * flingSensitivity);
   predictedOffset.Clamp(maxOffset);
   nsPoint pos = GetScrollPosition();
   nsPoint destinationPos = pos + predictedOffset;
   ScrollSnap(destinationPos, aMode);
 }
 
 void
-ScrollFrameHelper::FlingSnap(const mozilla::CSSPoint& aDestination)
-{
-  ScrollSnap(CSSPoint::ToAppUnits(aDestination));
-}
-
-void
 ScrollFrameHelper::ScrollSnap(const nsPoint &aDestination,
                               nsIScrollableFrame::ScrollMode aMode)
 {
   nsRect scrollRange = GetScrollRangeForClamping();
   nsPoint pos = GetScrollPosition();
   nsPoint snapDestination = scrollRange.ClampPoint(aDestination);
   if (GetSnapPointForDestination(nsIScrollableFrame::DEVICE_PIXELS,
                                                  pos,

--- a/layout/generic/nsGfxScrollFrame.h
+++ b/layout/generic/nsGfxScrollFrame.h
@@ -199,17 +199,16 @@ public:
       mScrollPort.XMost() - mScrolledFrame->GetRect().XMost();
     pt.y = mScrollPort.y - mScrolledFrame->GetPosition().y;
     return pt;
   }
   nsRect GetScrollRange() const;
   // Get the scroll range assuming the scrollport has size (aWidth, aHeight).
   nsRect GetScrollRange(nscoord aWidth, nscoord aHeight) const;
   nsSize GetScrollPositionClampingScrollPortSize() const;
-  void FlingSnap(const mozilla::CSSPoint& aDestination);
   void ScrollSnap(nsIScrollableFrame::ScrollMode aMode = nsIScrollableFrame::SMOOTH_MSD);
   void ScrollSnap(const nsPoint &aDestination,
                   nsIScrollableFrame::ScrollMode aMode = nsIScrollableFrame::SMOOTH_MSD);
 
 protected:
   nsRect GetScrollRangeForClamping() const;
 
 public:
@@ -836,19 +835,16 @@ public:
   virtual void ScrollBy(nsIntPoint aDelta, ScrollUnit aUnit, ScrollMode aMode,
                         nsIntPoint* aOverflow, nsIAtom* aOrigin = nullptr,
                         nsIScrollableFrame::ScrollMomentum aMomentum = nsIScrollableFrame::NOT_MOMENTUM,
                         nsIScrollbarMediator::ScrollSnapMode aSnap
                           = nsIScrollbarMediator::DISABLE_SNAP)
                         override {
     mHelper.ScrollBy(aDelta, aUnit, aMode, aOverflow, aOrigin, aMomentum, aSnap);
   }
-  virtual void FlingSnap(const mozilla::CSSPoint& aDestination) override {
-    mHelper.FlingSnap(aDestination);
-  }
   virtual void ScrollSnap() override {
     mHelper.ScrollSnap();
   }
   /**
    * @note This method might destroy the frame, pres shell and other objects.
    */
   virtual void ScrollToRestoredPosition() override {
     mHelper.ScrollToRestoredPosition();
@@ -1251,19 +1247,16 @@ public:
   virtual void ScrollBy(nsIntPoint aDelta, ScrollUnit aUnit, ScrollMode aMode,
                         nsIntPoint* aOverflow, nsIAtom* aOrigin = nullptr,
                         nsIScrollableFrame::ScrollMomentum aMomentum = nsIScrollableFrame::NOT_MOMENTUM,
                         nsIScrollbarMediator::ScrollSnapMode aSnap
                           = nsIScrollbarMediator::DISABLE_SNAP)
                         override {
     mHelper.ScrollBy(aDelta, aUnit, aMode, aOverflow, aOrigin, aMomentum, aSnap);
   }
-  virtual void FlingSnap(const mozilla::CSSPoint& aDestination) override {
-    mHelper.FlingSnap(aDestination);
-  }
   virtual void ScrollSnap() override {
     mHelper.ScrollSnap();
   }
   /**
    * @note This method might destroy the frame, pres shell and other objects.
    */
   virtual void ScrollToRestoredPosition() override {
     mHelper.ScrollToRestoredPosition();

--- a/layout/generic/nsIScrollableFrame.h
+++ b/layout/generic/nsIScrollableFrame.h
@@ -267,26 +267,16 @@ public:
                         nsIntPoint* aOverflow = nullptr,
                         nsIAtom* aOrigin = nullptr,
                         ScrollMomentum aMomentum = NOT_MOMENTUM,
                         nsIScrollbarMediator::ScrollSnapMode aSnap
                           = nsIScrollbarMediator::DISABLE_SNAP) = 0;
 
   /**
    * Perform scroll snapping, possibly resulting in a smooth scroll to
-   * maintain the scroll snap position constraints.  A predicted landing
-   * position determined by the APZC is used to select the best matching
-   * snap point, allowing touchscreen fling gestures to navigate between
-   * snap points.
-   * @param aDestination The desired landing position of the fling, which
-   * is used to select the best matching snap point.
-   */
-  virtual void FlingSnap(const mozilla::CSSPoint& aDestination) = 0;
-  /**
-   * Perform scroll snapping, possibly resulting in a smooth scroll to
    * maintain the scroll snap position constraints.  Velocity sampled from
    * main thread scrolling is used to determine best matching snap point
    * when called after a fling gesture on a trackpad or mouse wheel.
    */
   virtual void ScrollSnap() = 0;
 
   /**
    * @note This method might destroy the frame, pres shell and other objects.