Add trace event for DrawingBuffer::prepareMailbox in blink category.

third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp

 /*
  * Copyright (c) 2010, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 234 matching lines @@
         // 1. WebGL draws something.
         // 2. The compositor begins the frame.
         // 3. Javascript makes a context lost using WEBGL_lose_context extension.
         // 4. Here.
         return false;
     }
     ASSERT(!m_isHidden);
     if (!m_contentsChanged)
         return false;
 
+    TRACE_EVENT0("blink", "DrawingBuffer::prepareMailbox");
+
     if (m_newMailboxCallback)
         (*m_newMailboxCallback)();
 
     // Resolve the multisampled buffer into m_colorBuffer texture.
     if (m_antiAliasingMode != None)
         commit();
 
     if (bitmap) {
         bitmap->setSize(size());
 
@@ skipping 844 matching lines @@
 
 void DrawingBuffer::restoreTextureBindings()
 {
     // This class potentially modifies the bindings for GL_TEXTURE_2D and
     // GL_TEXTURE_RECTANGLE. Only GL_TEXTURE_2D needs to be restored since
     // the public interface for WebGL does not support GL_TEXTURE_RECTANGLE.
     m_gl->BindTexture(GL_TEXTURE_2D, m_texture2DBinding);
 }
 
 } // namespace blink