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

content/browser/browsing_instance.h

 // Copyright (c) 2011 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.
 
 #ifndef CONTENT_BROWSER_BROWSING_INSTANCE_H_
 #define CONTENT_BROWSER_BROWSING_INSTANCE_H_
 #pragma once
 
 #include "base/hash_tables.h"
 #include "base/lazy_instance.h"
@@ skipping 32 matching lines @@
 // one SiteInstance per site for the entire browser context, not just for each
 // BrowsingInstance.  This reduces the number of renderer processes we create.
 // (This is currently only true if --process-per-site is specified at the
 // command line.)
 //
 // A BrowsingInstance is live as long as any SiteInstance has a reference to
 // it.  A SiteInstance is live as long as any NavigationEntry or RenderViewHost
 // have references to it.  Because both classes are RefCounted, they do not
 // need to be manually deleted.
 //
-// Currently, the BrowsingInstance class is not visible outside of the
-// SiteInstance class.  To get a new SiteInstance that is part of the same
-// BrowsingInstance, use SiteInstance::GetRelatedSiteInstance.  Because of
-// this, BrowsingInstances and SiteInstances are tested together in
+// BrowsingInstance has no public members, as it is designed to be
+// visible only from the SiteInstance class.  To get a new
+// SiteInstance that is part of the same BrowsingInstance, use
+// SiteInstance::GetRelatedSiteInstance.  Because of this,
+// BrowsingInstances and SiteInstances are tested together in
 // site_instance_unittest.cc.
 //
 ///////////////////////////////////////////////////////////////////////////////
 class CONTENT_EXPORT BrowsingInstance
     : public base::RefCounted<BrowsingInstance> {
- public:
+ protected:
   // Create a new BrowsingInstance.
   explicit BrowsingInstance(content::BrowserContext* context);
 
   // Returns whether the process-per-site model is in use (globally or just for
   // the given url), in which case we should ensure there is only one
   // SiteInstance per site for the entire browser context, not just for this
   // BrowsingInstance.
   virtual bool ShouldUseProcessPerSite(const GURL& url);
 
   // Get the browser context to which this BrowsingInstance belongs.
-  content::BrowserContext* browser_context() { return browser_context_; }
+  content::BrowserContext* browser_context() const { return browser_context_; }
 
   // Returns whether this BrowsingInstance has registered a SiteInstance for
   // the site of the given URL.
   bool HasSiteInstance(const GURL& url);
 
   // Get the SiteInstance responsible for rendering the given URL.  Should
   // create a new one if necessary, but should not create more than one
   // SiteInstance per site.
   SiteInstance* GetSiteInstanceForURL(const GURL& url);
 
   // Adds the given SiteInstance to our map, to ensure that we do not create
   // another SiteInstance for the same site.
   void RegisterSiteInstance(SiteInstance* site_instance);
 
   // Removes the given SiteInstance from our map, after all references to it
   // have been deleted.  This means it is safe to create a new SiteInstance
   // if the user later visits a page from this site, within this
   // BrowsingInstance.
   void UnregisterSiteInstance(SiteInstance* site_instance);
 
- protected:
+  friend class SiteInstance;
+
   friend class base::RefCounted<BrowsingInstance>;
 
   // Virtual to allow tests to extend it.
   virtual ~BrowsingInstance();
 
  private:
   // Map of site to SiteInstance, to ensure we only have one SiteInstance per
   typedef base::hash_map<std::string, SiteInstance*> SiteInstanceMap;
 
   // Map of BrowserContext to SiteInstanceMap, for use in the process-per-site
@@ skipping 30 matching lines @@
   // Global map of BrowserContext to SiteInstanceMap, for process-per-site.
   static base::LazyInstance<
       ContextSiteInstanceMap,
       base::LeakyLazyInstanceTraits<ContextSiteInstanceMap> >
           context_site_instance_map_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowsingInstance);
 };
 
 #endif  // CONTENT_BROWSER_BROWSING_INSTANCE_H_