CC Animation: Unify ElementId in Blink Compositor Worker.

cc/layers/layer.cc

 // Copyright 2010 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/layers/layer.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 1699 matching lines @@
   num_descendants_that_draw_content_ += num;
   SetNeedsCommit();
   if (parent())
     parent()->AddDrawableDescendants(num);
 }
 
 void Layer::RunMicroBenchmark(MicroBenchmark* benchmark) {
   benchmark->RunOnLayer(this);
 }
 
-void Layer::SetElementId(uint64_t id) {
+void Layer::SetElementId(ElementId id) {
   DCHECK(IsPropertyChangeAllowed());
   if (element_id_ == id)
     return;
   TRACE_EVENT1(TRACE_DISABLED_BY_DEFAULT("compositor-worker"),
                "Layer::SetElementId", "id", id);
   element_id_ = id;
   SetNeedsCommit();
 }
 
 void Layer::SetMutableProperties(uint32_t properties) {
@@ skipping 21 matching lines @@
       ->data.num_copy_requests_in_subtree;
 }
 
 gfx::Transform Layer::screen_space_transform() const {
   DCHECK_NE(transform_tree_index_, -1);
   return draw_property_utils::ScreenSpaceTransform(
       this, layer_tree_host_->property_trees()->transform_tree);
 }
 
 }  // namespace cc