mac content shell drt: Do not force the mesa gl implementation.

content/common/gpu/image_transport_surface_mac.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 "content/common/gpu/image_transport_surface.h"
 
 #include "base/mac/scoped_cftyperef.h"
 #include "base/memory/scoped_ptr.h"
 #include "content/common/gpu/gpu_messages.h"
 #include "content/common/gpu/texture_image_transport_surface.h"
@@ skipping 418 matching lines @@
       case gfx::kGLImplementationAppleGL:
         if (!io_surface_support) {
           DLOG(WARNING) << "No IOSurface support";
           return NULL;
         } else {
           surface = new IOSurfaceImageTransportSurface(
               manager, stub, surface_handle.handle);
         }
         break;
       default:
-        NOTREACHED();
+        NOTREACHED() << gfx::GetGLImplementation();

[Ken Russell (switch to Gerrit), 2013/02/26 20:25:29]

This could be more descriptive.

         return NULL;
     }
   }
   if (surface->Initialize())
     return surface;
   else
     return NULL;
 }
 
 }  // namespace content