cc : Rebuild property trees when opacity changes only if its required.

cc/trees/layer_tree_host.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_host.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 518 matching lines @@
 
   // This must happen after synchronizing property trees and after push
   // properties, which updates property tree indices.
   sync_tree->UpdatePropertyTreeScrollingAndAnimationFromMainThread();
 
   // This must happen after synchronizing property trees and after pushing
   // properties, which updates the clobber_active_value flag.
   sync_tree->UpdatePropertyTreeScrollOffset(&property_trees_);
 
   micro_benchmark_controller_.ScheduleImplBenchmarks(host_impl);
-  // We don't track changes to effect tree on main thread. But, to preserve any
-  // change tracking done on active tree's effect tree, we copy it to the main
-  // thread's effect tree before we push the main thread property trees to
-  // active tree.
-  if (property_trees_changed_on_active_tree)
-    property_trees_.ResetAllChangeTracking(
-        PropertyTrees::ResetFlags::ALL_TREES);
-  else
-    property_trees_.ResetAllChangeTracking(
-        PropertyTrees::ResetFlags::TRANSFORM_TREE);

[jaydasika, 2016/05/17 01:40:01]

TRANSFORM_TREE flag is used only here outside tests. I will remove it in a
follow-up

+  property_trees_.ResetAllChangeTracking(PropertyTrees::ResetFlags::ALL_TREES);
 }
 
 void LayerTreeHost::WillCommit() {
   OnCommitForSwapPromises();
   client_->WillCommit();
 }
 
 void LayerTreeHost::UpdateHudLayer() {
   if (debug_state_.ShowHudInfo()) {
     if (!hud_layer_.get()) {
@@ skipping 1101 matching lines @@
   int seq_num = property_trees_.sequence_number;
   LayerTreeHostCommon::CallFunctionForEveryLayer(this, [seq_num](Layer* layer) {
     layer->set_property_tree_sequence_number(seq_num);
   });
 
   surface_id_namespace_ = proto.surface_id_namespace();
   next_surface_sequence_ = proto.next_surface_sequence();
 }
 
 }  // namespace cc