[Sync] Add support for enabling/disabling an extension before it's installed

chrome/browser/extensions/extension_service.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 CHROME_BROWSER_EXTENSIONS_EXTENSION_SERVICE_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_SERVICE_H_
 #pragma once
 
 #include <map>
 #include <set>
@@ skipping 258 matching lines @@
   // to ExtensionPrefs some other way.
   virtual bool UninstallExtension(const std::string& extension_id,
                                   bool external_uninstall,
                                   std::string* error);
 
   virtual bool IsExtensionEnabled(
       const std::string& extension_id) const OVERRIDE;
   virtual bool IsExternalExtensionUninstalled(
       const std::string& extension_id) const OVERRIDE;
 
-  // Enable or disable an extension. No action if the extension is already
-  // enabled/disabled.
+  // Enables the extension.  If the extension is already enabled, does
+  // nothing.
   virtual void EnableExtension(const std::string& extension_id);
+
+  // Disables the extension.  If the extension is already disabled, or
+  // cannot be disabled, does nothing.
   virtual void DisableExtension(const std::string& extension_id);
 
   // Updates the |extension|'s granted permissions lists to include all
   // permissions in the |extension|'s manifest.
   void GrantPermissions(const Extension* extension);
 
   // Updates the |extension|'s granted permissions lists to include all
   // permissions in the |extension|'s manifest and re-enables the
   // extension.
   void GrantPermissionsAndEnableExtension(const Extension* extension);
@@ skipping 381 matching lines @@
   NaClModuleInfoList nacl_module_list_;
 
   FRIEND_TEST_ALL_PREFIXES(ExtensionServiceTest,
                            InstallAppsWithUnlimtedStorage);
   FRIEND_TEST_ALL_PREFIXES(ExtensionServiceTest,
                            InstallAppsAndCheckStorageProtection);
   DISALLOW_COPY_AND_ASSIGN(ExtensionService);
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_SERVICE_H_