Make sure GetAuthenticatedAccountId() returns a canonicalized id.

components/signin/core/browser/profile_oauth2_token_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 COMPONENTS_SIGNIN_CORE_BROWSER_PROFILE_OAUTH2_TOKEN_SERVICE_H_
 #define COMPONENTS_SIGNIN_CORE_BROWSER_PROFILE_OAUTH2_TOKEN_SERVICE_H_
 
 #include <string>
 
 #include "base/gtest_prod_util.h"
@@ skipping 75 matching lines @@
 
   // Simply returns NULL and should be overriden by subsclasses.
   virtual net::URLRequestContextGetter* GetRequestContext() override;
 
   // Updates the internal cache of the result from the most-recently-completed
   // auth request (used for reporting errors to the user).
   virtual void UpdateAuthError(
       const std::string& account_id,
       const GoogleServiceAuthError& error) override;
 
+  // Validate that the account_id argument is valid.  This method DCHECKs
+  // when invalid.
+  void ValidateAccountId(const std::string& account_id) const;
+
  private:
   // The client with which this instance was initialized, or NULL.
   SigninClient* client_;
 
   // Used to expose auth errors to the UI.
   scoped_ptr<SigninErrorController> signin_error_controller_;
 
   DISALLOW_COPY_AND_ASSIGN(ProfileOAuth2TokenService);
 };
 
 #endif  // COMPONENTS_SIGNIN_CORE_BROWSER_PROFILE_OAUTH2_TOKEN_SERVICE_H_