GPU: Add trace for real SwapBuffers.

ui/gl/gl_surface_nsview.mm

 // Copyright (c) 2012 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 "ui/gl/gl_surface_nsview.h"
 
 #import <AppKit/NSOpenGL.h>
 #import <AppKit/NSView.h>
 
+#include "base/debug/trace_event.h"
 #include "ui/gl/gl_context_nsview.h"
 
 namespace gfx {
 
 GLSurfaceNSView::GLSurfaceNSView(AcceleratedWidget view)
     : view_(view),
       context_(NULL) {
 }
 
 GLSurfaceNSView::~GLSurfaceNSView() {
 }
 
 void GLSurfaceNSView::Destroy() {
 }
 
 bool GLSurfaceNSView::IsOffscreen() {
   return false;
 }
 
 bool GLSurfaceNSView::SwapBuffers() {
+  TRACE_EVENT2("gpu", "GLSurfaceNSView:RealSwapBuffers",
+      "width", GetSize().width(),
+      "height", GetSize().height());
   context_->FlushBuffer();
   return true;
 }
 
 gfx::Size GLSurfaceNSView::GetSize() {
   return gfx::Size(NSSizeToCGSize([view_ bounds].size));
 }
 
 void* GLSurfaceNSView::GetHandle() {
   return view_;
 }
 
 bool GLSurfaceNSView::OnMakeCurrent(GLContext* context) {
   context_ = static_cast<GLContextNSView *>(context);
   return true;
 }
 
 }  // namespace gfx