Add some trace events to Sky compositor

sky/compositor/layer.cc

 // Copyright 2014 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 "sky/compositor/layer.h"
 
+#include "base/debug/trace_event.h"
 #include "mojo/skia/ganesh_surface.h"
 #include "sky/compositor/layer_host.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 
 namespace sky {
 
 Layer::Layer(LayerClient* client) : client_(client), host_(nullptr) {
 }
 
 Layer::~Layer() {
 }
 
 void Layer::ClearClient() {
   client_ = nullptr;
 }
 
 void Layer::SetSize(const gfx::Size& size) {
   size_ = size;
 }
 
 void Layer::Display() {
+  TRACE_EVENT0("sky", "Layer::Display");
+
   DCHECK(host_);
 
   mojo::GaneshSurface surface(host_->ganesh_context(),
                               host_->resource_manager()->CreateTexture(size_));
 
   SkCanvas* canvas = surface.canvas();
 
   gfx::Rect rect(size_);
   client_->PaintContents(canvas, rect);
   canvas->flush();
 
   texture_ = surface.TakeTexture();
 }
 
 scoped_ptr<mojo::GLTexture> Layer::GetTexture() {
   return texture_.Pass();
 }
 
 }  // namespace sky