Hack to restrict runtime API to dev channel rather than experimental.

chrome/renderer/resources/extensions/experimental.runtime_custom_bindings.js

-// Copyright (c) 2012 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.
-
-// Custom bindings for the runtime API.
-
-var extensionNatives = requireNative('extension');
-var GetExtensionViews = extensionNatives.GetExtensionViews;
-var chromeHidden = requireNative('chrome_hidden').GetChromeHidden();
-var sendRequest = require('sendRequest').sendRequest;
-
-chromeHidden.registerCustomHook('experimental.runtime', function(bindingsAPI) {
-  var apiFunctions = bindingsAPI.apiFunctions;
-
-  apiFunctions.setCustomCallback('getBackgroundPage',
-                                 function(name, request, response) {
-    if (request.callback) {
-      var bg = GetExtensionViews(-1, 'BACKGROUND')[0] || null;
-      request.callback(bg);
-    }
-    request.callback = null;
-  });
-});