Identity API: Add chrome.identity.onSignInChanged routing and IDL

chrome/common/extensions/api/identity.idl

 // Copyright (c) 2013 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.
 
 // Use the <code>chrome.identity</code> API to get OAuth2 access tokens.
 namespace identity {
 
   dictionary TokenDetails {
     // Fetching a token may require the user to sign-in to Chrome, or
     // approve the application's requested scopes. If the interactive
@@ skipping 21 matching lines @@
     // loading a page meant to be displayed.
     //
     // If the interactive flag is <code>true</code>, the window will
     // be displayed when a page load completes. If the flag is
     // <code>false</code> or omitted, <code>launchWebAuthFlow</code>
     // will return with an error if the initial navigation does not
     // complete the flow.
     boolean? interactive;
   };
 
+  dictionary AccountInfo {
+    // A unique identifier for the account. This ID will not change
+    // for the lifetime of the account.
+    DOMString id;
+    // The email address associated with the account. APIs that return
+    // <code>AccountInfo</code> objects will populate this field if
+    // the app has the <code>identity.email</code> permission.
+    DOMString? email;
+  };
+
   callback GetAuthTokenCallback = void (optional DOMString token);
   callback InvalidateAuthTokenCallback = void ();
   callback LaunchWebAuthFlowCallback = void (optional DOMString responseUrl);
 
   interface Functions {
     // Gets an OAuth2 access token using the client ID and scopes
     // specified in the <a
     // href="app_identity.html#update_manifest"><code>oauth2</code>
     // section of manifest.json</a>.
     //
@@ skipping 26 matching lines @@
     // first URL in the provider's auth flow. When the provider
     // redirects to a URL matching the pattern
     // <code>https://&lt;app-id&gt;.chromiumapp.org/*</code>, the
     // window will close, and the final redirect URL will be passed to
     // the <var>callback</var> function.
     //
     // |details| : WebAuth flow options.
     // |callback| : Called with the URL redirected back to your application.
     static void launchWebAuthFlow(WebAuthFlowDetails details,
                                   LaunchWebAuthFlowCallback callback);
-  }
-  ;
+  };
+
+  interface Events {
+    // Fired when signin state changes for an account on the user's profile.
+    static void onSignInChanged(AccountInfo account, boolean signedIn);
+  };
 };