cc: Make LayerAnimationController keep state for clearing scroll delta

cc/animation/layer_animation_controller.h

Index: cc/animation/layer_animation_controller.h
diff --git a/cc/animation/layer_animation_controller.h b/cc/animation/layer_animation_controller.h
index d776ee9cbd7de72e27eca1722cf6dcfd75ca797a..25c8f38722fa7d40d2c023332b776184863a4b27 100644
--- a/cc/animation/layer_animation_controller.h
+++ b/cc/animation/layer_animation_controller.h
@@ -139,6 +139,16 @@ class CC_EXPORT LayerAnimationController
   // be computed.
   bool MaximumTargetScale(float* max_scale) const;
 
+  // When a scroll animation is removed on the main thread, its compositor

[aelias_OOO_until_Jul13, 2015/01/21 21:23:52]

I'd add the comment "This is to provide the illusion of synchronicity to JS that
simultaneously removes an animation and sets the scroll offset."

[ajuma, 2015/01/21 21:50:27]

Done.

+  // thread counterpart continues producing scroll deltas until activation.
+  // These scroll deltas need to be cleared at activation, so that the active
+  // layer's scroll offset matches the offset provided by the main thread
+  // rather than a combination of this offset and scroll deltas produced by
+  // the removed animation.
+  bool clear_scroll_delta_for_removed_animation() const {

[aelias_OOO_until_Jul13, 2015/01/21 21:23:52]

Could you rename this and the field to "animation_was_interrupted"?  I'd rather
be declarative rather than imperative in the naming, it's the layer's job to
decide what to do as a result of the removed animation (and maybe we'll come up
with a different policy on this at some point).

[ajuma, 2015/01/21 21:50:27]

Done.

+    return clear_scroll_delta_for_removed_animation_;
+  }
+
   bool needs_to_start_animations_for_testing() {
     return needs_to_start_animations_;
   }
@@ -156,8 +166,7 @@ class CC_EXPORT LayerAnimationController
       LayerAnimationController* controller_impl) const;
   void RemoveAnimationsCompletedOnMainThread(
       LayerAnimationController* controller_impl) const;
-  void PushPropertiesToImplThread(
-      LayerAnimationController* controller_impl) const;
+  void PushPropertiesToImplThread(LayerAnimationController* controller_impl);
 
   void StartAnimations(base::TimeTicks monotonic_time);
   void PromoteStartedAnimations(base::TimeTicks monotonic_time,
@@ -191,8 +200,6 @@ class CC_EXPORT LayerAnimationController
 
   void NotifyObserversAnimationWaitingForDeletion();
 
-  void NotifyObserversScrollOffsetAnimationRemoved();
-
   bool HasValueObserver();
   bool HasActiveValueObserver();
 
@@ -216,6 +223,8 @@ class CC_EXPORT LayerAnimationController
   // previous attempt at starting animations failed to start all animations.
   bool needs_to_start_animations_;
 
+  bool clear_scroll_delta_for_removed_animation_;
+
   DISALLOW_COPY_AND_ASSIGN(LayerAnimationController);
 };