Clean up renderer fling code.

This cl cleans up the fling handling logic on the renderer side. I've already
added DCHECKs in InputHandlerProxy::HandleGestureFlingStart and some other
functions in input_handler_proxy.cc to make sure that touchscreen and touchpad
flings are not sent to the renderer. Since Mar 28, Autoscroll fling is also
being handled in browser (https://chromium-review.googlesource.com/980965) and
it is safe to delete the dead code from renderer.

To avoid making this cl larger I'll land separate cls for the remaining clean up:
1-Convert fling related layout tests that are using event sender to use gpu
benchmarking or write browser tests instead, delete send GFS/GFC from event sender.
2-DidOvercroll and DidStopFlinging IPCs are not needed anymore.
3-git grep for "fling" and "curve" and check code coverage to remove any remaining
fling related dead code.

Bug: 249063
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: Ibd1db260c0b3c92c7ccf17156dd38c4865ae1926
Reviewed-on: https://chromium-review.googlesource.com/1117639
Commit-Queue: Sahel Sharify <sahel@chromium.org>
Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Reviewed-by: David Bokan <bokan@chromium.org>
Reviewed-by: Timothy Dresser <tdresser@chromium.org>
Reviewed-by: Lan Wei <lanwei@chromium.org>
Cr-Commit-Position: refs/heads/master@{#574244}

cc/input/input_handler.h

@@ -62,7 +62,6 @@ class CC_EXPORT InputHandlerClient {
 
   virtual void WillShutdown() = 0;
   virtual void Animate(base::TimeTicks time) = 0;
-  virtual void MainThreadHasStoppedFlinging() = 0;
   virtual void ReconcileElasticOverscrollAndRootScroll() = 0;
   virtual void UpdateRootLayerStateForSynchronousInputHandler(
       const gfx::ScrollOffset& total_scroll_offset,
@@ -164,10 +163,6 @@ class CC_EXPORT InputHandler {
   // ScrollBegin() returned SCROLL_STARTED.
   virtual InputHandlerScrollResult ScrollBy(ScrollState* scroll_state) = 0;
 
-  // Returns SCROLL_STARTED if a layer was actively being scrolled,
-  // SCROLL_IGNORED if not.
-  virtual ScrollStatus FlingScrollBegin() = 0;
-
   virtual void MouseMoveAt(const gfx::Point& mouse_position) = 0;
   virtual void MouseDown() = 0;
   virtual void MouseUp() = 0;

cc/test/fake_proxy.h

@@ -33,7 +33,6 @@ class FakeProxy : public Proxy {
   bool RequestedAnimatePending() override;
   void NotifyInputThrottledUntilCommit() override {}
   void SetDeferCommits(bool defer_commits) override {}
-  void MainThreadHasStoppedFlinging() override {}
   bool CommitRequested() const override;
   void Start() override {}
   void Stop() override {}

cc/trees/layer_tree_host.cc

@@ -267,10 +267,6 @@ void LayerTreeHost::BeginMainFrame(const viz::BeginFrameArgs& args) {
   client_->BeginMainFrame(args);
 }
 
-void LayerTreeHost::DidStopFlinging() {
-  proxy_->MainThreadHasStoppedFlinging();
-}
-
 const LayerTreeDebugState& LayerTreeHost::GetDebugState() const {
   return debug_state_;
 }

cc/trees/layer_tree_host.h

@@ -223,10 +223,6 @@ class CC_EXPORT LayerTreeHost : public MutatorHostClient {
   // the compositor thread.
   const base::WeakPtr<InputHandler>& GetInputHandler() const;
 
-  // Informs the compositor that an active fling gesture being processed on the
-  // main thread has been finished.
-  void DidStopFlinging();
-
   // Debugging and benchmarks ---------------------------------
   void SetDebugState(const LayerTreeDebugState& debug_state);
   const LayerTreeDebugState& GetDebugState() const;

cc/trees/layer_tree_host_impl.cc

@@ -1255,12 +1255,6 @@ DrawResult LayerTreeHostImpl::CalculateRenderPasses(FrameData* frame) {
   return draw_result;
 }
 
-void LayerTreeHostImpl::MainThreadHasStoppedFlinging() {
-  browser_controls_offset_manager_->MainThreadHasStoppedFlinging();
-  if (input_handler_client_)
-    input_handler_client_->MainThreadHasStoppedFlinging();
-}
-
 void LayerTreeHostImpl::DidAnimateScrollOffset() {
   client_->SetNeedsCommitOnImplThread();
   client_->RenewTreePriority();
@@ -4442,20 +4436,6 @@ void LayerTreeHostImpl::ScrollEnd(ScrollState* scroll_state, bool should_snap) {
   ScrollEndImpl(scroll_state);
 }
 
-InputHandler::ScrollStatus LayerTreeHostImpl::FlingScrollBegin() {
-  InputHandler::ScrollStatus scroll_status;
-  scroll_status.main_thread_scrolling_reasons =
-      MainThreadScrollingReason::kNotScrollingOnMain;
-  if (!CurrentlyScrollingNode()) {
-    scroll_status.thread = SCROLL_IGNORED;
-    scroll_status.main_thread_scrolling_reasons =
-        MainThreadScrollingReason::kNoScrollingLayer;
-  } else {
-    scroll_status.thread = SCROLL_ON_IMPL_THREAD;
-  }
-  return scroll_status;
-}
-
 void LayerTreeHostImpl::MouseDown() {
   ScrollbarAnimationController* animation_controller =
       ScrollbarAnimationControllerForElementId(

cc/trees/layer_tree_host_impl.h

@@ -254,7 +254,6 @@ class CC_EXPORT LayerTreeHostImpl
   void SetSynchronousInputHandlerRootScrollOffset(
       const gfx::ScrollOffset& root_offset) override;
   void ScrollEnd(ScrollState* scroll_state, bool should_snap = false) override;
-  InputHandler::ScrollStatus FlingScrollBegin() override;
 
   void MouseDown() override;
   void MouseUp() override;
@@ -315,7 +314,6 @@ class CC_EXPORT LayerTreeHostImpl
   void ActivateAnimations();
   void Animate();
   void AnimatePendingTreeAfterCommit();
-  void MainThreadHasStoppedFlinging();
   void DidAnimateScrollOffset();
   void SetFullViewportDamage();
   void SetViewportDamage(const gfx::Rect& damage_rect);