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

cc/animation/animation_player_unittest.cc

Index: cc/animation/animation_player_unittest.cc
diff --git a/cc/animation/animation_player_unittest.cc b/cc/animation/animation_player_unittest.cc
index 81f9e34f1876c48d81f37bdefdc855d09528391a..edcb9995b1f7be19eccfbc375a38642af0c3882e 100644
--- a/cc/animation/animation_player_unittest.cc
+++ b/cc/animation/animation_player_unittest.cc
@@ -79,6 +79,11 @@ class LayerTreeMutatorsClientTest : public LayerTreeMutatorsClient {
     SetLayerMutated(layer_id, active_tree, Animation::TRANSFORM);
   }
 
+  void ScrollOffsetAnimationFinished() override {}
+  gfx::ScrollOffset GetScrollOffsetForAnimation(int layer_id) const override {
+    return gfx::ScrollOffset();
+  }
+
   void SetLayerScrollOffsetMutated(
       int layer_id,
       bool active_tree,