Fix ExtensionServiceTest.ClearExtensionData flakiness

chrome/browser/extensions/extension_service.h

 // Copyright (c) 2012 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_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 246 matching lines @@
   // currently has any window showing.
   // Allows noisy failures.
   void ReloadExtension(const std::string& extension_id);
 
   // Suppresses noisy failures.
   void ReloadExtensionWithQuietFailure(const std::string& extension_id);
 
   // Uninstalls the specified extension. Callers should only call this method
   // with extensions that exist. |reason| lets the caller specify why the
   // extension is uninstalled.
+  //
+  // If the return value is true, |deletion_done_callback| is invoked when data
+  // deletion is done or at least is scheduled.
   virtual bool UninstallExtension(const std::string& extension_id,
                                   extensions::UninstallReason reason,
+                                  const base::Closure& deletion_done_callback,
                                   base::string16* error);
 
   // 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,
@@ skipping 442 matching lines @@
                            GreylistedExtensionDisabled);
   FRIEND_TEST_ALL_PREFIXES(ExtensionServiceTest,
                            GreylistDontEnableManuallyDisabled);
   FRIEND_TEST_ALL_PREFIXES(ExtensionServiceTest,
                            GreylistUnknownDontChange);
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionService);
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_SERVICE_H_