diff --git a/static/js/framework/externs.js b/static/js/framework/externs.js
new file mode 100644
index 0000000..a0375a1
--- /dev/null
+++ b/static/js/framework/externs.js
@@ -0,0 +1,25 @@
+/* Copyright 2016 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 or at
+ * https://developers.google.com/open-source/licenses/bsd
+ */
+
+/** @type {CS.env} */
+var CS_env;
+
+// Exported functions must be mentioned in this externs file so that JSCompiler
+// will allow exporting functions by writing '_hideID = CS_hideID'.
+var _hideID;
+var _showID;
+var _hideEl;
+var _showEl;
+var _showInstead;
+var _toggleHidden;
+var _toggleCollapse;
+var _CS_dismissCue;
+var _CS_updateProjects;
+var _CP_checkProjectName;
+var _TKR_toggleStar;
+var _TKR_toggleStarLocal;
+var _TKR_syncStarIcons;