Prune shared extendion module after extension updating.

chrome/browser/extensions/shared_module_service.h

 // Copyright 2014 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 CHROME_BROWSER_EXTENSIONS_SHARED_MODULE_SERVICE_H_
 #define CHROME_BROWSER_EXTENSIONS_SHARED_MODULE_SERVICE_H_
 
 #include <list>
 
 #include "base/scoped_observer.h"
@@ skipping 37 matching lines @@
 
   // Checks an extension's shared module imports to see if they are satisfied.
   // If they are not, this function adds the dependencies to the pending install
   // list if |extension| came from the webstore.
   ImportStatus SatisfyImports(const Extension* extension);
 
   // Returns a set of extensions that import a given extension.
   scoped_ptr<ExtensionSet> GetDependentExtensions(const Extension* extension);
 
  private:
+  // Uninstall shared modules which are not used by other extensions.
+  void PruneSharedModules();
+
   // ExtensionRegistryObserver implementation.
+  virtual void OnExtensionInstalled(content::BrowserContext* browser_context,
+                                    const Extension* extension,
+                                    bool is_update) OVERRIDE;
   virtual void OnExtensionUninstalled(content::BrowserContext* browser_context,
                                       const Extension* extension) OVERRIDE;
 
   ScopedObserver<ExtensionRegistry, ExtensionRegistryObserver>
       extension_registry_observer_;
 
   // The context associated with this SharedModuleService.
   content::BrowserContext* browser_context_;
 
   DISALLOW_COPY_AND_ASSIGN(SharedModuleService);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_SHARED_MODULE_SERVICE_H_