Make sure GetAuthenticatedAccountId() returns a canonicalized id.

components/signin/core/browser/profile_oauth2_token_service.h

Index: components/signin/core/browser/profile_oauth2_token_service.h
diff --git a/components/signin/core/browser/profile_oauth2_token_service.h b/components/signin/core/browser/profile_oauth2_token_service.h
index b6f133f946a6bd23c10ef2c8f9484ffde0499d34..fbc1fccc5a4ef8ffa0c49cb4fe462c2ea77c7f37 100644
--- a/components/signin/core/browser/profile_oauth2_token_service.h
+++ b/components/signin/core/browser/profile_oauth2_token_service.h
@@ -93,6 +93,10 @@ class ProfileOAuth2TokenService : public OAuth2TokenService,
       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_;