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 087818492754d27afc20e5536e605807d285859e..d88c40ce9f2f4c73c9bc1670146f75a881a54931 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_;