Re-fix http://crbug.com/87176, and add a test.

content/test/test_render_view_host_factory.cc

 // Copyright (c) 2012 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/test/test_render_view_host_factory.h"
 
 #include "content/browser/renderer_host/test_render_view_host.h"
 #include "content/browser/site_instance_impl.h"
 #include "content/public/browser/render_process_host_factory.h"
 
 namespace content {
 
 TestRenderViewHostFactory::TestRenderViewHostFactory(
-    RenderProcessHostFactory* rph_factory)
-    : render_process_host_factory_(rph_factory) {
+    RenderProcessHostFactory* rph_factory) {
+  SiteInstanceImpl::set_render_process_host_factory(rph_factory);
   RenderViewHostFactory::RegisterFactory(this);
 }
 
 TestRenderViewHostFactory::~TestRenderViewHostFactory() {
   RenderViewHostFactory::UnregisterFactory();
+  SiteInstanceImpl::set_render_process_host_factory(NULL);
 }
 
 void TestRenderViewHostFactory::set_render_process_host_factory(
     RenderProcessHostFactory* rph_factory) {
-  render_process_host_factory_ = rph_factory;
+  SiteInstanceImpl::set_render_process_host_factory(rph_factory);
 }
 
 RenderViewHost* TestRenderViewHostFactory::CreateRenderViewHost(
     SiteInstance* instance,
     RenderViewHostDelegate* delegate,
     RenderWidgetHostDelegate* widget_delegate,
     int routing_id,
     int main_frame_routing_id,
     bool swapped_out,
     SessionStorageNamespace* session_storage) {
-  // See declaration of render_process_host_factory_ below.
-  static_cast<SiteInstanceImpl*>(instance)->
-      set_render_process_host_factory(render_process_host_factory_);
   return new TestRenderViewHost(
       instance, delegate, widget_delegate, routing_id, main_frame_routing_id,
       swapped_out);
 }
 
 }  // namespace content