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

cc/animation/element_animations.cc

 // 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.
 
 #include "cc/animation/element_animations.h"
 
 #include "cc/animation/animation_host.h"
 #include "cc/animation/animation_player.h"
 #include "cc/animation/animation_registrar.h"
 #include "cc/animation/layer_animation_value_observer.h"
@@ skipping 19 matching lines @@
 
   void OnTransformAnimated(const gfx::Transform& transform) override {
     element_animations_->SetTransformMutated(tree_type_, transform);
   }
 
   void OnScrollOffsetAnimated(const gfx::ScrollOffset& scroll_offset) override {
     element_animations_->SetScrollOffsetMutated(tree_type_, scroll_offset);
   }
 
   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 tree_type_ == LayerTreeType::ACTIVE; }
 
  private:
   ElementAnimations* element_animations_;
   const LayerTreeType tree_type_;
 
   DISALLOW_COPY_AND_ASSIGN(ValueObserver);
 };
@@ skipping 178 matching lines @@
     Animation::TargetProperty target_property,
     int group) {
   for (PlayersListNode* node = players_list_->head();
        node != players_list_->end(); node = node->next()) {
     AnimationPlayer* player = node->value();
     player->NotifyAnimationFinished(monotonic_time, target_property, group);
   }
 }
 
 gfx::ScrollOffset ElementAnimations::ScrollOffsetForAnimation() const {
-  // TODO(loyso): implement it.
+  DCHECK(layer_animation_controller_);
+  if (animation_host()) {
+    DCHECK(animation_host()->mutator_host_client());
+    return animation_host()->mutator_host_client()->GetScrollOffsetForAnimation(
+        layer_id());
+  }
+
   return gfx::ScrollOffset();
 }
 
 }  // namespace cc