Add support for app_shell-only extension APIs

extensions/shell/common/api/shell_identity.idl

Index: extensions/shell/common/api/shell_identity.idl
diff --git a/extensions/shell/common/api/shell_identity.idl b/extensions/shell/common/api/shell_identity.idl
new file mode 100644
index 0000000000000000000000000000000000000000..6772baed5c0b4fdd5a4addc9520b80ecf15f5f24
--- /dev/null
+++ b/extensions/shell/common/api/shell_identity.idl
@@ -0,0 +1,14 @@
+// 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.
+
+// Use the <code>chrome.shell.identity</code> API to retrieve OAuth2 tokens
+// for user accounts.  See also <code>chrome.identity</code>.
+namespace shell.identity {
+
+  interface Functions {
+    // TODO(jamescook): Implement this with options and a callback.
+    static void getAuthToken();
+  };
+
+};