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 603ffa97e939d10368c37a6d7808cce02ececd20..e6677bb1cd7cf5961fd11d8e348108840404d7ac 100644
--- a/cc/animation/animation_player.cc
+++ b/cc/animation/animation_player.cc
@@ -119,6 +119,9 @@ void AnimationPlayer::UnbindElementAnimations() {
 }
 
 void AnimationPlayer::AddAnimation(scoped_ptr<Animation> animation) {
+  DCHECK(animation->target_property() != Animation::SCROLL_OFFSET ||
+         (animation_host_ && animation_host_->SupportsScrollAnimations()));
+
   if (element_animations_) {
     element_animations_->layer_animation_controller()->AddAnimation(
         animation.Pass());