Reland: Refactor code that defers extension background page loading

extensions/browser/extension_registry.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_EXTENSION_REGISTRY_H_
 #define EXTENSIONS_BROWSER_EXTENSION_REGISTRY_H_
 
 #include <string>
 
 #include "base/compiler_specific.h"
@@ skipping 25 matching lines @@
     BLACKLISTED = 1 << 3,
     EVERYTHING = (1 << 4) - 1,
   };
 
   explicit ExtensionRegistry(content::BrowserContext* browser_context);
   virtual ~ExtensionRegistry();
 
   // Returns the instance for the given |browser_context|.
   static ExtensionRegistry* Get(content::BrowserContext* browser_context);
 
+  content::BrowserContext* browser_context() const { return browser_context_; }
+
   // NOTE: These sets are *eventually* mututally exclusive, but an extension can
   // appear in two sets for short periods of time.
   const ExtensionSet& enabled_extensions() const {
     return enabled_extensions_;
   }
   const ExtensionSet& disabled_extensions() const {
     return disabled_extensions_;
   }
   const ExtensionSet& terminated_extensions() const {
     return terminated_extensions_;
@@ skipping 105 matching lines @@
   ObserverList<ExtensionRegistryObserver> observers_;
 
   content::BrowserContext* const browser_context_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionRegistry);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_EXTENSION_REGISTRY_H_