cc: Add some tracing below LayerTreeHost::PushProperties.

cc/layers/picture_layer.cc

Index: cc/layers/picture_layer.cc
diff --git a/cc/layers/picture_layer.cc b/cc/layers/picture_layer.cc
index 284f2a382c7f2102bf7863ef62f9d316e4087c0d..f9df22cd9b8d67e5e7ba0ac82073426c978ef7eb 100644
--- a/cc/layers/picture_layer.cc
+++ b/cc/layers/picture_layer.cc
@@ -5,6 +5,7 @@
 #include "cc/layers/picture_layer.h"
 
 #include "base/auto_reset.h"
+#include "base/trace_event/trace_event.h"
 #include "cc/layers/content_layer_client.h"
 #include "cc/layers/picture_layer_impl.h"
 #include "cc/playback/display_list_recording_source.h"
@@ -50,6 +51,7 @@ scoped_ptr<LayerImpl> PictureLayer::CreateLayerImpl(LayerTreeImpl* tree_impl) {
 
 void PictureLayer::PushPropertiesTo(LayerImpl* base_layer) {
   Layer::PushPropertiesTo(base_layer);
+  TRACE_EVENT0("cc", "PictureLayer::PushPropertiesTo");
   PictureLayerImpl* layer_impl = static_cast<PictureLayerImpl*>(base_layer);
   // TODO(danakj): Make is_mask_ a constructor parameter for PictureLayer.
   DCHECK_EQ(layer_impl->is_mask(), is_mask_);