Add a function triggering extension installed to ExtensionRegistryObserver

chrome/browser/extensions/install_tracker.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 CHROME_BROWSER_EXTENSIONS_INSTALL_TRACKER_H_
 #define CHROME_BROWSER_EXTENSIONS_INSTALL_TRACKER_H_
 
 #include "base/observer_list.h"
 #include "base/prefs/pref_change_registrar.h"
 #include "base/scoped_observer.h"
@@ skipping 35 matching lines @@
   void OnBeginCrxInstall(const std::string& extension_id);
   void OnFinishCrxInstall(const std::string& extension_id, bool success);
   void OnInstallFailure(const std::string& extension_id);
 
   // Overriddes for KeyedService.
   virtual void Shutdown() OVERRIDE;
 
  private:
   void OnAppsReordered();
 
-  // content::NotificationObserver.
+  // content::NotificationObserver implementation.
   virtual void Observe(int type,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
   // ExtensionRegistryObserver implementation.
   virtual void OnExtensionLoaded(content::BrowserContext* browser_context,
                                  const Extension* extension) OVERRIDE;
   virtual void OnExtensionUnloaded(
       content::BrowserContext* browser_context,
       const Extension* extension,
       UnloadedExtensionInfo::Reason reason) OVERRIDE;
+  virtual void OnExtensionWillBeInstalled(
+      content::BrowserContext* browser_context,
+      const Extension* extension,
+      bool is_update,
+      const std::string& old_name) OVERRIDE;
 
   ObserverList<InstallObserver> observers_;
   content::NotificationRegistrar registrar_;
   PrefChangeRegistrar pref_change_registrar_;
 
-  // Listen to extension load, unloaded notifications.
   ScopedObserver<ExtensionRegistry, ExtensionRegistryObserver>
       extension_registry_observer_;
 
   DISALLOW_COPY_AND_ASSIGN(InstallTracker);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_INSTALL_TRACKER_H_