Make TokenService drop its ref to WebDataService in Shutdown() rather than dtor.

chrome/browser/signin/token_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.
 //
 // The TokenService will supply authentication tokens for any service that
 // needs it, such as sync. Whenever the user logs in, a controller watching
 // the token service is expected either to call ClientLogin to derive a new
 // SID and LSID, or to use GAIA OAuth requests to derive an OAuth1 access
 // token for the OAuthLogin scope.  Whenever such credentials are available,
 // the TokenService should be updated with new credentials.  The controller
@@ skipping 84 matching lines @@
     TokenRequestFailedDetails(const std::string& service,
                               const GoogleServiceAuthError& error)
         : service_(service), error_(error) {}
     const std::string& service() const { return service_; }
     const GoogleServiceAuthError& error() const { return error_; }
    private:
     std::string service_;
     GoogleServiceAuthError error_;
   };
 
+  // ProfileKeyedService implementation.
+  virtual void Shutdown() OVERRIDE;
+
   // Methods to register or remove SigninDiagnosticObservers
   void AddSigninDiagnosticsObserver(
       signin_internals_util::SigninDiagnosticsObserver* observer);
   void RemoveSigninDiagnosticsObserver(
       signin_internals_util::SigninDiagnosticsObserver* observer);
 
   // Initialize this token service with a request source
   // (usually from a GaiaAuthConsumer constant), and the profile.
   // Typically you'd then update the credentials.
   void Initialize(const char* const source, Profile* profile);
@@ skipping 138 matching lines @@
 
   friend class TokenServiceTest;
   FRIEND_TEST_ALL_PREFIXES(TokenServiceTest, LoadTokensIntoMemoryBasic);
   FRIEND_TEST_ALL_PREFIXES(TokenServiceTest, LoadTokensIntoMemoryAdvanced);
   FRIEND_TEST_ALL_PREFIXES(TokenServiceTest, FullIntegrationNewServicesAdded);
 
   DISALLOW_COPY_AND_ASSIGN(TokenService);
 };
 
 #endif  // CHROME_BROWSER_SIGNIN_TOKEN_SERVICE_H_