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

The default for the context's backing FBO is 0. If the context does have an internal FBO,
it can return it so that glBindFramebuffer(0) will not detach the texture from it.

Review URL: http://codereview.chromium.org/5987004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@69879 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index e93624ce..ad33868f 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -2737,6 +2737,8 @@
     } else {
       service_id = info->service_id();
     }
+  } else {
+    service_id = context_->GetBackingFrameBufferObject();
   }
 
   if (target == GL_FRAMEBUFFER || target == GL_DRAW_FRAMEBUFFER_EXT) {