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

cc/trees/layer_tree_host.cc

Index: cc/trees/layer_tree_host.cc
diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index 9ab367896bb704950d2679505aefb47ad2abc2c8..d0f344ff203f7c357e38b7b450408c35eb1a645d 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -536,16 +536,7 @@ void LayerTreeHost::FinishCommitOnImplThread(LayerTreeHostImpl* host_impl) {
   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() {