gl: Move platform-specific EGL code into separate files

ui/gl/gl_surface_x11.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 "ui/gl/gl_surface.h"
 
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 322 matching lines @@
       return surface;
     }
     case kGLImplementationMockGL:
       return new GLSurfaceStub;
     default:
       NOTREACHED();
       return NULL;
   }
 }
 
+EGLNativeDisplayType GetPlatformDefaultEGLNativeDisplay() {
+  return base::MessagePumpForUI::GetDefaultXDisplay();
+}
+
 }  // namespace gfx