Change GPU process to use IO rather than UI MessageLoop on Mac OS. On this platform, the GPU proces…

content/gpu/gpu_main.cc

 // 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 <stdlib.h>
 
 #if defined(OS_WIN)
 #include <windows.h>
 #endif
 
@@ skipping 168 matching lines @@
     // For windows, if the target_services interface is not zero, the process
     // is sandboxed and we must call LowerToken() before rendering untrusted
     // content.
     sandbox::TargetServices* target_services =
         parameters.sandbox_info->target_services;
     if (target_services)
       target_services->LowerToken();
   }
 #endif
 
-  MessageLoop::Type message_loop_type = MessageLoop::TYPE_UI;
+  MessageLoop::Type message_loop_type = MessageLoop::TYPE_IO;
 #if defined(OS_WIN)
   // Unless we're running on desktop GL, we don't need a UI message
   // loop, so avoid its use to work around apparent problems with some
   // third-party software.
-  message_loop_type = MessageLoop::TYPE_IO;
   if (command_line.HasSwitch(switches::kUseGL) &&
       command_line.GetSwitchValueASCII(switches::kUseGL) ==
           gfx::kGLImplementationDesktopName) {
       message_loop_type = MessageLoop::TYPE_UI;
   }
 #elif defined(OS_LINUX)
   message_loop_type = MessageLoop::TYPE_DEFAULT;
 #endif
 
   MessageLoop main_message_loop(message_loop_type);
   base::PlatformThread::SetName("CrGpuMain");
 
   GpuProcess gpu_process;
 
   GpuChildThread* child_thread = new GpuChildThread(dead_on_arrival, gpu_info);
 
   child_thread->Init(start_time);
 
   gpu_process.set_main_thread(child_thread);
 
   {
     TRACE_EVENT0("gpu", "Run Message Loop");
     main_message_loop.Run();
   }
 
   child_thread->StopWatchdog();
 
   return 0;
 }