Hide BrowsingInstance from all but SiteInstance, as intended by design.

content/browser/site_instance.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/browser/site_instance.h"
 
 #include "base/command_line.h"
 #include "content/browser/browsing_instance.h"
 #include "content/browser/child_process_security_policy.h"
 #include "content/browser/renderer_host/render_process_host_impl.h"
@@ skipping 123 matching lines @@
   if (IsURLSameAsAnySiteInstance(url))
     return false;
 
   // If the site URL is an extension (e.g., for hosted apps or WebUI) but the
   // process is not (or vice versa), make sure we notice and fix it.
   GURL site_url = GetSiteForURL(browsing_instance_->browser_context(), url);
   return !RenderProcessHostImpl::IsSuitableHost(
       process_, browsing_instance_->browser_context(), site_url);
 }
 
+content::BrowserContext* SiteInstance::GetBrowserContext() const {
+  return browsing_instance_->browser_context();
+}
+
 /*static*/
 SiteInstance* SiteInstance::CreateSiteInstance(
     content::BrowserContext* browser_context) {
   return new SiteInstance(new BrowsingInstance(browser_context));
 }
 
 /*static*/
 SiteInstance* SiteInstance::CreateSiteInstanceForURL(
     content::BrowserContext* browser_context, const GURL& url) {
   // This BrowsingInstance may be deleted if it returns an existing
@@ skipping 86 matching lines @@
 
 void SiteInstance::LockToOrigin() {
   const CommandLine& command_line = *CommandLine::ForCurrentProcess();
   if (command_line.HasSwitch(switches::kEnableStrictSiteIsolation)) {
     ChildProcessSecurityPolicy* policy =
         ChildProcessSecurityPolicy::GetInstance();
     policy->LockToOrigin(process_->GetID(), site_);
   }
 }