GLContextNSView should not assume concrete type GLSurface is GLSurfaceNSView

ui/gfx/gl/gl_context_mac.mm

 // Copyright (c) 2011 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 "base/basictypes.h"
 #include "base/logging.h"
 #include "base/mac/mac_util.h"
 #include "base/memory/scoped_generic_obj.h"
 #include "base/memory/scoped_ptr.h"
 #include "third_party/mesa/MesaLib/include/GL/osmesa.h"
@@ skipping 25 matching lines @@
 class GLShareGroup;
 
 scoped_refptr<GLContext> GLContext::CreateGLContext(
     GLShareGroup* share_group,
     GLSurface* compatible_surface,
     GpuPreference gpu_preference) {
   switch (GetGLImplementation()) {
     case kGLImplementationDesktopGL: {
       scoped_refptr<GLContext> context;
 #if defined(USE_AURA)
-      DCHECK(!compatible_surface->IsOffscreen());
-      context = new GLContextNSView(share_group);
+      if (compatible_surface->IsOffscreen())
+        context = new GLContextCGL(share_group);
+      else
+        context = new GLContextNSView(share_group);
+#else
+      context = new GLContextCGL(share_group);
+#endif // USE_AURA
       if (!context->Initialize(compatible_surface, gpu_preference))
         return NULL;
-#else
-      context = new GLContextCGL(share_group);
-      if (!context->Initialize(compatible_surface, gpu_preference))
-        return NULL;
-#endif // USE_AURA
 
       return context;
     }
     case kGLImplementationOSMesaGL: {
       scoped_refptr<GLContext> context(new GLContextOSMesa(share_group));
       if (!context->Initialize(compatible_surface, gpu_preference))
         return NULL;
 
       return context;
     }
@@ skipping 80 matching lines @@
   }
 
   if (found_online && found_offline) {
     supports_dual_gpus = true;
   }
 
   return supports_dual_gpus;
 }
 
 }  // namespace gfx