Hotword: Fix always-on case by removing MS_CONFIGURED timeout

chrome/browser/resources/hotword/nacl_manager.js

 // 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.
 
 cr.define('hotword', function() {
 'use strict';
 
 /**
  * Class used to manage the state of the NaCl recognizer plugin. Handles all
  * control of the NaCl plugin, including creation, start, stop, trigger, and
@@ skipping 442 matching lines @@
 /**
  * Handle a MODEL_LOADED message from the plugin.
  * The plugin sends this message after successfully loading the language model.
  * @private
  */
 NaClManager.prototype.handleModelLoaded_ = function() {
   if (this.recognizerState_ != ManagerState_.LOADING) {
     return;
   }
   this.sendDataToPlugin_(this.stream_.getAudioTracks()[0]);
-  this.waitForMessage_(hotword.constants.TimeoutMs.LONG,
-                       hotword.constants.NaClPlugin.MS_CONFIGURED);
+  // The plugin will send a MS_CONFIGURED, but don't set a timeout waiting for
+  // it. After the recent MediaStreamAudioTrack refactoring, the behavior of

[Matt Giuca, 2016/09/08 03:50:45]

The code should describe what it is *now*, not refer to what it was (which will
become less and less relevant as time goes on). Especially avoid time-sensitive
terms like "recent".

It would be good to move the discussion of recent changes to the commit log
rather than the code.

For the code comments, how about:
"The plugin will send a MS_CONFIGURED, but don't set a timeout waiting for it.
MediaStreamAudioTrack::Configure() will remain pending until the first audio
buffer is received. When the audio source is a DSP for always-on detection, no
audio sample is sent until the DSP detects a potential hotword trigger. Thus,
Configure would remain pending indefinitely if we were to wait here. See
https://crbug.com/616203."

(Note also: I added "https://" to the URL so it is clickable in some editors.)

+  // MediaStreamAudioTrack::Configure() changed where it remains pending until
+  // the first audio buffer is received. When the audio source is a DSP for
+  // always-on detection, no audio sample is sent until the DSP detects a
+  // potential hotword trigger. Thus, Configure may remain pending indefinitely.
+  // See crbug.com/616203 for more info.
 };
 
 /**
  * Handle a MS_CONFIGURED message from the plugin.
  * The plugin sends this message after successfully configuring the audio input
  * stream.
  * @private
  */
 NaClManager.prototype.handleMsConfigured_ = function() {
   if (this.recognizerState_ != ManagerState_.LOADING) {
@@ skipping 113 matching lines @@
         break;
     }
   }
 };
 
 return {
   NaClManager: NaClManager
 };
 
 });