CC Animation: Use ElementId to attach CC animation players.

cc/test/layer_tree_host_common_test.cc

Index: cc/test/layer_tree_host_common_test.cc
diff --git a/cc/test/layer_tree_host_common_test.cc b/cc/test/layer_tree_host_common_test.cc
index 4f2be2b4fc4b57165cd0513f05eb8c8a3edb84b2..ef0cfc5b266ebbd5ba29fb3965bf3710266fb1a6 100644
--- a/cc/test/layer_tree_host_common_test.cc
+++ b/cc/test/layer_tree_host_common_test.cc
@@ -226,6 +226,20 @@ bool LayerTreeHostCommonTestBase::UpdateLayerListContains(int id) const {
   return false;
 }
 
+scoped_refptr<Layer> LayerTreeHostCommonTestBase::CreateTestLayer() {
+  auto layer = Layer::Create();
+  layer->SetElementId(NextTestElementId());
+  return layer;
+}
+
+std::unique_ptr<LayerImpl> LayerTreeHostCommonTestBase::CreateTestLayerImpl(
+    LayerTreeImpl* tree_impl,
+    int id) {
+  auto layer = LayerImpl::Create(tree_impl, id);
+  layer->SetElementId(NextTestElementId());
+  return layer;
+}
+
 LayerTreeHostCommonTest::LayerTreeHostCommonTest()
     : LayerTreeHostCommonTestBase(LayerTreeSettings()) {}