Add LogOut method to GaiaCookieManagerService::Observer.

components/signin/core/browser/gaia_cookie_manager_service.cc

Index: components/signin/core/browser/gaia_cookie_manager_service.cc
diff --git a/components/signin/core/browser/gaia_cookie_manager_service.cc b/components/signin/core/browser/gaia_cookie_manager_service.cc
index cb807f69f377eabea044767f4491ad512ee971c9..de75979164ac5291a8e3a09d98ac7c57f0867f12 100644
--- a/components/signin/core/browser/gaia_cookie_manager_service.cc
+++ b/components/signin/core/browser/gaia_cookie_manager_service.cc
@@ -666,8 +666,10 @@ void GaiaCookieManagerService::OnLogOutSuccess() {
   VLOG(1) << "GaiaCookieManagerService::OnLogOutSuccess";
 
   list_accounts_stale_ = true;
-
   fetcher_backoff_.InformOfRequest(true);
+  FOR_EACH_OBSERVER(Observer, observer_list_,
+                    OnLogOutAccountsFromCookieCompleted(
+                        GoogleServiceAuthError(GoogleServiceAuthError::NONE)));
   HandleNextRequest();
 }
 
@@ -687,6 +689,8 @@ void GaiaCookieManagerService::OnLogOutFailure(
     return;
   }
 
+  FOR_EACH_OBSERVER(Observer, observer_list_,
+                    OnLogOutAccountsFromCookieCompleted(error));
   HandleNextRequest();
 }