cc : Add OnTransformAnimated to transform tree

cc/trees/layer_tree_impl.cc

 // Copyright 2011 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/trees/layer_tree_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 490 matching lines @@
 }
 
 LayerImplList::reverse_iterator LayerTreeImpl::rbegin() {
   return layer_list_.rbegin();
 }
 
 LayerImplList::reverse_iterator LayerTreeImpl::rend() {
   return layer_list_.rend();
 }
 
-LayerImpl* LayerTreeImpl::LayerByElementId(ElementId element_id) const {
+int LayerTreeImpl::LayerIdByElementId(ElementId element_id) const {
   auto iter = element_layers_map_.find(element_id);
   if (iter == element_layers_map_.end())
-    return nullptr;
+    return Layer::INVALID_ID;
 
   return iter->second;
 }
 
+LayerImpl* LayerTreeImpl::LayerByElementId(ElementId element_id) const {

[ajuma, 2016/08/23 23:40:12]

Just to make sure, this will go away once all the current callers are converted
to talk directly to property tree nodes? If so, please leave a TODO.

[jaydasika, 2016/08/24 00:13:42]

Done.

+  return LayerById(LayerIdByElementId(element_id));
+}
+
 void LayerTreeImpl::AddToElementMap(LayerImpl* layer) {
   if (!layer->element_id())
     return;
 
   TRACE_EVENT2(TRACE_DISABLED_BY_DEFAULT("compositor-worker"),
                "LayerTreeImpl::AddToElementMap", "element",
                layer->element_id().AsValue().release(), "layer_id",
                layer->id());
 
-  element_layers_map_[layer->element_id()] = layer;
+  element_layers_map_[layer->element_id()] = layer->id();
 
   layer_tree_host_impl_->animation_host()->RegisterElement(
       layer->element_id(),
       IsActiveTree() ? ElementListType::ACTIVE : ElementListType::PENDING);
 }
 
 void LayerTreeImpl::RemoveFromElementMap(LayerImpl* layer) {
   if (!layer->element_id())
     return;
 
@@ skipping 1538 matching lines @@
 
 void LayerTreeImpl::ResetAllChangeTracking() {
   layers_that_should_push_properties_.clear();
   // Iterate over all layers, including masks and replicas.
   for (auto& layer : *layers_)
     layer->ResetChangeTracking();
   property_trees_.ResetAllChangeTracking();
 }
 
 }  // namespace cc