CC Animations: Port Impl-only-scrolling to use compositor animation timelines.

cc/animation/animation_player.cc

Index: cc/animation/animation_player.cc
diff --git a/cc/animation/animation_player.cc b/cc/animation/animation_player.cc
index a5e0e64f2207cb4f4d0bdda128d64107eaae178d..a00e7394219295f9a5d87853f40b589f48d37a70 100644
--- a/cc/animation/animation_player.cc
+++ b/cc/animation/animation_player.cc
@@ -37,7 +37,8 @@ class AnimationPlayer::ValueObserver : public LayerAnimationValueObserver {
   }
 
   void OnAnimationWaitingForDeletion() override {
-    // TODO(loyso): implement it.
+    // TODO(loyso): See Layer::OnAnimationWaitingForDeletion. But we always do
+    // PushProperties for AnimationTimelines for now.
   }
 
   bool IsActive() const override { return is_active_; }
@@ -170,6 +171,8 @@ void AnimationPlayer::LayerUnregistered(int layer_id, bool is_active_tree) {
 
 void AnimationPlayer::AddAnimation(scoped_ptr<Animation> animation) {
   DCHECK(layer_animation_controller_);
+  DCHECK(animation->target_property() != Animation::SCROLL_OFFSET ||
+         !animation_host_ || animation_host_->GetSupportsScrollAnimations());
   layer_animation_controller_->AddAnimation(animation.Pass());
   SetNeedsCommit();
 }
@@ -288,7 +291,14 @@ void AnimationPlayer::DestroyPendingValueObserver() {
 }
 
 gfx::ScrollOffset AnimationPlayer::ScrollOffsetForAnimation() const {
-  // TODO(loyso): implement it.
+  DCHECK(layer_id_);
+  if (animation_host()) {
+    DCHECK(animation_host()->layer_tree_mutators_client());
+    return animation_host()
+        ->layer_tree_mutators_client()
+        ->GetScrollOffsetForAnimation(layer_id_);
+  }
+
   return gfx::ScrollOffset();
 }