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

app/gfx/gl/gl_context.cc

 // Copyright (c) 2009 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 <string>
 
 #include "app/app_switches.h"
 #include "app/gfx/gl/gl_context.h"
 #include "app/gfx/gl/gl_bindings.h"
 #include "app/gfx/gl/gl_implementation.h"
 #include "base/command_line.h"
 #include "base/logging.h"
 
 namespace gfx {
 
+unsigned int GLContext::GetBackingFrameBufferObject() {
+  return 0;
+}
+
 std::string GLContext::GetExtensions() {
   DCHECK(IsCurrent());
   const char* ext = reinterpret_cast<const char*>(glGetString(GL_EXTENSIONS));
   return std::string(ext ? ext : "");
 }
 
 bool GLContext::HasExtension(const char* name) {
   std::string extensions = GetExtensions();
   extensions += " ";
 
@@ skipping 19 matching lines @@
   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
   if (glGetError() != GL_NO_ERROR) {
     LOG(ERROR) << "glClear failed.";
     return false;
   }
 
   return true;
 }
 
 }  // namespace gfx