bluetooth: Basic browser tests for chrome://bluetooth-internals.

chrome/browser/resources/bluetooth_internals/interfaces.js

 // 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.
 
 /**
  * Javascript for Mojo interface helpers and global variables, served from
  *     chrome://bluetooth-internals/.
  */
 
 cr.define('interfaces', function() {
@@ skipping 46 matching lines @@
       adapter = interfaces.Connection.bindHandleToProxy(
           response.adapter,
           interfaces.BluetoothAdapter.Adapter);
 
       Object.assign(interfaces, {
         DefaultAdapter: adapter,
       });
     });
   }
 
-  var initialized = false;
-  var initializePromise = null;
+  /**
+  * Overriden by tests to give them a chance to setup a fake Mojo browser proxy
+  * before any other code executes.
+  * @return {!Promise} A promise firing once necessary setup has been completed.
+  */
+  var setupFn = window.setupFn || function() { return Promise.resolve(); };
 
   function initialize() {
-    if (initialized) {
-      return Promise.resolve();
-    }
-
-    if (initializePromise) {
-      return initializePromise;
-    }
-
-    initializePromise = initializeProxies().then(function() {
-      initialized = true;
-    });
-
-    return initializePromise;
+    return setupFn().then(initializeProxies);
   }
 
   return {
     initialize: initialize,
   };
 });