Gracefully handle being signed out of a supervised profile.

This is not something that would happen under normal circumstances, but it may happen if the preferences become corrupted or are modified.

BUG=321370

Review URL: https://codereview.chromium.org/138243004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245242 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/signin/mutable_profile_oauth2_token_service.cc

@@ -251,7 +251,13 @@ void MutableProfileOAuth2TokenService::UpdateAuthError(
   }
 #endif
 
-  DCHECK_GT(refresh_tokens_.count(account_id), 0u);
+  if (refresh_tokens_.count(account_id) == 0) {
+    // This could happen if the preferences have been corrupted (see
+    // http://crbug.com/321370). In a Debug build that would be a bug, but in a
+    // Release build we want to deal with it gracefully.
+    NOTREACHED();
+    return;
+  }
   refresh_tokens_[account_id]->SetLastAuthError(error);
 }