Map the render process's glBindFramebuffer(0) to the context's backing FBO....

gpu/command_buffer/service/gles2_cmd_decoder.cc

 // Copyright (c) 2010 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 "gpu/command_buffer/service/gles2_cmd_decoder.h"
 
 #include <stdio.h>
 
 #include <algorithm>
 #include <list>
@@ skipping 2719 matching lines @@
       // It's a new id so make a framebuffer info for it.
       glGenFramebuffersEXT(1, &service_id);
       CreateFramebufferInfo(client_id, service_id);
       info = GetFramebufferInfo(client_id);
       IdAllocator* id_allocator =
           group_->GetIdAllocator(id_namespaces::kFramebuffers);
       id_allocator->MarkAsUsed(client_id);
     } else {
       service_id = info->service_id();
     }
+  } else {
+    service_id = context_->GetBackingFrameBufferObject();
   }
 
   if (target == GL_FRAMEBUFFER || target == GL_DRAW_FRAMEBUFFER_EXT) {
     bound_draw_framebuffer_ = info;
   }
   if (target == GL_FRAMEBUFFER || target == GL_READ_FRAMEBUFFER_EXT) {
     bound_read_framebuffer_ = info;
   }
 
   // When rendering to an offscreen frame buffer, instead of unbinding from
@@ skipping 3249 matching lines @@
   return error::kNoError;
 }
 
 // Include the auto-generated part of this file. We split this because it means
 // we can easily edit the non-auto generated parts right here in this file
 // instead of having to edit some template or the code generator.
 #include "gpu/command_buffer/service/gles2_cmd_decoder_autogen.h"
 
 }  // namespace gles2
 }  // namespace gpu