[Extensions] Propagate activeTab hosts to extension background pages

extensions/browser/process_manager.h

 // Copyright 2013 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 EXTENSIONS_BROWSER_PROCESS_MANAGER_H_
 #define EXTENSIONS_BROWSER_PROCESS_MANAGER_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 55 matching lines @@
   // for example for hosted apps and extensions that aren't enabled in
   // Incognito.
   virtual bool CreateBackgroundHost(const Extension* extension,
                                     const GURL& url);
 
   // Gets the ExtensionHost for the background page for an extension, or NULL if
   // the extension isn't running or doesn't have a background page.
   ExtensionHost* GetBackgroundHostForExtension(const std::string& extension_id);
 
   // Returns the SiteInstance that the given URL belongs to.
+  // Callers should wrap the result in a scoped_refptr to ensure the
+  // SiteInstance becomes refcounted.
+  // TODO(devlin): The above comment clearly indicates that this should just
+  // return a refptr. Update callers.
   // TODO(aa): This only returns correct results for extensions and packaged
   // apps, not hosted apps.
   virtual content::SiteInstance* GetSiteInstanceForURL(const GURL& url);
 
   // If the view isn't keeping the lazy background page alive, increments the
   // keepalive count to do so.
   void AcquireLazyKeepaliveCountForView(
       content::RenderViewHost* render_view_host);
 
   // If the view is keeping the lazy background page alive, decrements the
@@ skipping 213 matching lines @@
 
   // Must be last member, see doc on WeakPtrFactory.
   base::WeakPtrFactory<ProcessManager> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ProcessManager);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_PROCESS_MANAGER_H_