cc: Switch RenderingStats collection in Layer::Update() to RenderingStatsInstrumentation

cc/layers/layer.cc

Index: cc/layers/layer.cc
diff --git a/cc/layers/layer.cc b/cc/layers/layer.cc
index b07b30855615920ac9295c4587306604f527af76..b41912bab49a270cef7c1a810235fad4ea7fc61d 100644
--- a/cc/layers/layer.cc
+++ b/cc/layers/layer.cc
@@ -817,4 +817,9 @@ ScrollbarLayer* Layer::ToScrollbarLayer() {
   return NULL;
 }
 
+RenderingStatsInstrumentation* Layer::rendering_stats_instrumentation() const {
+  CHECK(layer_tree_host());

[egraether, 2013/03/23 00:15:40]

I'm not sure what's best here. Should I just store a reference to
RenderingStatsInstrumentation on Layer? Or can we assume that it's only used
when a LayerTreeHost is set?

[danakj, 2013/03/23 01:56:32]

We won't update() when there's no LayerTreeHost, so I think you should go
through that.

+  return layer_tree_host()->rendering_stats_instrumentation();
+}
+
 }  // namespace cc