Fix smooth scroll jump when switching scroll handling between MT and CC

third_party/WebKit/Source/platform/scroll/ScrollAnimatorCompositorCoordinator.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ScrollAnimatorCompositorCoordinator_h
 #define ScrollAnimatorCompositorCoordinator_h
 
 #include "platform/PlatformExport.h"
 #include "platform/heap/Handle.h"
 #include "public/platform/WebCompositorAnimationDelegate.h"
 #include "public/platform/WebCompositorAnimationPlayerClient.h"
 #include "wtf/Allocator.h"
 #include "wtf/Noncopyable.h"
 #include "wtf/OwnPtr.h"
 
 namespace blink {
 
 class ScrollableArea;
 class WebCompositorAnimationPlayer;
 class WebCompositorAnimationTimeline;
 
 class PLATFORM_EXPORT ScrollAnimatorCompositorCoordinator : public NoBaseWillBeGarbageCollectedFinalized<ScrollAnimatorCompositorCoordinator>, private WebCompositorAnimationPlayerClient, WebCompositorAnimationDelegate {
     USING_FAST_MALLOC_WILL_BE_REMOVED(ScrollAnimatorCompositorCoordinator);
     WTF_MAKE_NONCOPYABLE(ScrollAnimatorCompositorCoordinator);
 public:
     virtual ~ScrollAnimatorCompositorCoordinator();
 
     bool hasAnimationThatRequiresService() const;
+    void clearMainThreadScrollingReasons(bool clear);
+
+    virtual bool hasRunningAnimation() const { return false; }
 
     virtual void resetAnimationState();
     virtual void cancelAnimation();
 
     virtual ScrollableArea* scrollableArea() const = 0;
     virtual void tickAnimation(double monotonicTime) = 0;
     virtual void updateCompositorAnimations() = 0;
     virtual void notifyCompositorAnimationFinished(int groupId) = 0;
     virtual void notifyCompositorAnimationAborted(int groupId) = 0;
     virtual void layerForCompositedScrollingDidChange(WebCompositorAnimationTimeline*) = 0;
@@ skipping 41 matching lines @@
         // Waiting to cancel the animation currently running on the compositor.
         // There is no pending animation to replace the canceled animation.
         WaitingToCancelOnCompositor
     };
 
     OwnPtr<WebCompositorAnimationPlayer> m_compositorPlayer;
     int m_compositorAnimationAttachedToLayerId;
     RunState m_runState;
     int m_compositorAnimationId;
     int m_compositorAnimationGroupId;
+
+private:
+    void clearMainThreadScrollingReasonsOnLayer();
+
+    bool m_clearMainThreadScrollingReasons;
 };
 
 } // namespace blink
 
 #endif // ScrollAnimatorCompositorCoordinator_h