bluetooth: Standardize Bluetooth adapter access in Adapter service.

chrome/browser/resources/bluetooth_internals/bluetooth_internals.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 bluetooth_internals.html, served from
  *     chrome://bluetooth-internals/.
  */
 
 /**
@@ skipping 15 matching lines @@
    * Prints removed device to console.
    * @param {!Object} device the device that was removed
    */
   deviceRemoved: function(device) {
     console.log('Device removed');
     console.log(device);
   }
 };
 
 (function() {
-  var adapter = null;
-  var adapterClient = null;
-  var adapterClientHandle = null;
+  var adapter, adapterClient;
 
   /**
    * TODO: Move to shared location. See crbug.com/652361.
    * Helper to convert callback-based define() API to a promise-based API.
    * @param {!Array<string>} moduleNames
    * @return {!Promise}
    */
   function importModules(moduleNames) {
     return new Promise(function(resolve, reject) {
       define(moduleNames, function(var_args) {
         resolve(Array.prototype.slice.call(arguments, 0));
       });
     });
   }
 
   /**
    * Initializes Mojo proxies for page and Bluetooth services.
-   * @return {!Promise}
+   * @return {!Promise} resolves if adapter is acquired, rejects if Bluetooth
+   *     is not supported.
    */
   function initializeProxies() {
     return importModules([
       'content/public/renderer/frame_interfaces',
       'device/bluetooth/public/interfaces/adapter.mojom',
       'mojo/public/js/connection',
     ]).then(function([frameInterfaces, bluetoothAdapter, connection]) {
       console.log('Loaded modules');
 
       // Hook up the instance properties.
       AdapterClient.prototype.__proto__ =
           bluetoothAdapter.AdapterClient.stubClass.prototype;
 
-      // Create a message pipe and bind one end to client
-      // implementation.
-      adapterClient = new AdapterClient();
-      adapterClientHandle = connection.bindStubDerivedImpl(adapterClient);
+      var adapterFactory = connection.bindHandleToProxy(
+          frameInterfaces.getInterface(bluetoothAdapter.AdapterFactory.name),
+          bluetoothAdapter.AdapterFactory);
 
-      adapter = connection.bindHandleToProxy(
-          frameInterfaces.getInterface(bluetoothAdapter.Adapter.name),
-          bluetoothAdapter.Adapter);
+      // Get an Adapter service.
+      return adapterFactory.getAdapter().then(function(response) {

[dpapad, 2016/10/06 17:13:32]

Nit (optional): You could avoid nesting Promise callbacks, by using chaining
instead, as follows:

function initializeProxies() {
  var bluetoothAdapter, connection;
  return importModules([...].then(function(modules) {
    var frameInterfaces;
    [frameInterfaces, bluetoothAdapter, connection] = modules;
    ...
    return adapterFactory.getAdapter();
  }).then(function(response) {
     if (!response.adapter) { ... }
     ...
     // use bluetoothAdapter, connection here
  });
}

[mbrunson, 2016/10/06 20:25:57]

This will be used in a future patch.

+          if (!response.adapter) {
+            throw new Error('Bluetooth Not Supported on this platform.');
+          }
 
-      adapter.setClient(adapterClientHandle);
+          adapter = connection.bindHandleToProxy(response.adapter,
+                                                 bluetoothAdapter.Adapter);
+
+          // Create a message pipe and bind one end to client
+          // implementation and the other to the Adapter service.
+          adapterClient = new AdapterClient();
+          adapter.setClient(connection.bindStubDerivedImpl(adapterClient));
+      });
     });
   }
 
   document.addEventListener('DOMContentLoaded', function() {
     initializeProxies()
       .then(function() { return adapter.getDevices(); })
-      .then(function(response) { console.log(response.devices); });
+      .then(function(response) { console.log(response.devices); })
+      .catch(function(error) { console.error(error); });
   });
 })();