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

cc/test/animation_timelines_test_common.h

Index: cc/test/animation_timelines_test_common.h
diff --git a/cc/test/animation_timelines_test_common.h b/cc/test/animation_timelines_test_common.h
index e17d9e5d95b1a897394665c5278c6a2b065f4eaf..1eb8fb07ddf754f81b1d0c5b49405ff2fc967e49 100644
--- a/cc/test/animation_timelines_test_common.h
+++ b/cc/test/animation_timelines_test_common.h
@@ -68,7 +68,7 @@ class TestLayer {
 
 class TestHostClient : public MutatorHostClient {
  public:
-  TestHostClient();
+  explicit TestHostClient(ThreadInstance thread_instance);
   ~TestHostClient();
 
   void ClearMutatedProperties();
@@ -94,6 +94,9 @@ class TestHostClient : public MutatorHostClient {
       LayerTreeType tree_type,
       const gfx::ScrollOffset& scroll_offset) override;
 
+  void ScrollOffsetAnimationFinished() override {}
+  gfx::ScrollOffset GetScrollOffsetForAnimation(int layer_id) const override;
+
   bool mutators_need_commit() const { return mutators_need_commit_; }
   void set_mutators_need_commit(bool need) { mutators_need_commit_ = need; }