Mac: Use appropriate mechanism to determine partial swap capability

content/common/gpu/image_transport_surface_fbo_mac.mm

 // Copyright 2014 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_fbo_mac.h"
 
 #include "content/common/gpu/gpu_messages.h"
 #include "content/common/gpu/image_transport_surface_calayer_mac.h"
 #include "content/common/gpu/image_transport_surface_iosurface_mac.h"
 #include "ui/base/cocoa/remote_layer_api.h"
@@ skipping 191 matching lines @@
 }
 
 bool ImageTransportSurfaceFBO::PostSubBuffer(
     int x, int y, int width, int height) {
   // Mac does not support sub-buffer swaps.
   NOTREACHED();
   return false;
 }
 
 bool ImageTransportSurfaceFBO::SupportsPostSubBuffer() {
-  return true;
+  return false;
 }
 
 gfx::Size ImageTransportSurfaceFBO::GetSize() {
   return pixel_size_;
 }
 
 void* ImageTransportSurfaceFBO::GetHandle() {
   return NULL;
 }
 
@@ skipping 174 matching lines @@
     return;
   }
 
   has_complete_framebuffer_ = true;
 
   glBindTexture(texture_target, previous_texture_id);
   // The FBO remains bound for this GL context.
 }
 
 }  // namespace content