app_shell: Extend identity API stub

extensions/shell/common/api/identity.idl

 // Copyright 2014 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.
 
 // Simplified implementation of the <code>chrome.identity</code> for app_shell.
 namespace identity {
 
   dictionary GetAuthTokenDetails {
     // Ignored parameter. Exists only for compatibility.
     boolean? interactive;
   };
 
+  dictionary InvalidTokenDetails {
+    // Ignored parameter. Exists only for compatibility.
+    DOMString? token;
+  };
+
   // Called with the OAuth2 access token on success or undefined on error.
   callback GetAuthTokenCallback = void (optional DOMString token);
+  
+  // Called by removeCachedAuthToken().
+  callback InvalidateAuthTokenCallback = void ();
 
   interface Functions {
     // Returns an OAuth2 access token for the current app_shell user for scopes
     // from the manifest. Does not prompt the user. 
     static void getAuthToken(GetAuthTokenDetails options,
                              GetAuthTokenCallback callback);
+
+    // Stub. Calls callback immediately because app_shell does not cache access
+    // tokens the way Chrome does.
+    static void removeCachedAuthToken(InvalidTokenDetails details,
+                                      InvalidateAuthTokenCallback callback);
   };
 
+  interface Events {
+    // Stub. Never fired because app_shell only supports a single user account.
+    static void onSignInChanged(object account, boolean signedIn);
+  };
 };