Play a chime when the hotword is triggered.

chrome/browser/resources/hotword/state_manager.js

Index: chrome/browser/resources/hotword/state_manager.js
diff --git a/chrome/browser/resources/hotword/state_manager.js b/chrome/browser/resources/hotword/state_manager.js
index 2727cbcd8af7cf76ee799f1d8790d071e2cc9d3a..764d2c099dd202f5b81f9d123d2a4195da6d1373 100644
--- a/chrome/browser/resources/hotword/state_manager.js
+++ b/chrome/browser/resources/hotword/state_manager.js
@@ -43,8 +43,19 @@ cr.define('hotword', function() {
      */
     this.sessionStartedCb_ = null;
 
+    /**
+     * Hotword trigger audio notification... a.k.a The Chime (tm).
+     * @private {!Audio}
+     */
+    this.chime_ = document.createElement('audio');
+
     // Get the initial status.
     chrome.hotwordPrivate.getStatus(this.handleStatus_.bind(this));
+
+    // Setup the chime and insert into the page.
+    this.chime_.src = chrome.extension.getURL(
+        hotword.constants.SHARED_MODULE_ROOT + '/audio/chime.wav');
+    document.body.appendChild(this.chime_);

[Dan Beam, 2014/09/23 03:43:13]

what happens if this fails to load?

[Anand Mistry (off Chromium), 2014/09/24 01:35:02]

There'll be a warning on the console for this extension that the file couldn't
be found. But since this extension is hidden from the user unless they pass
--show-component-extension-options, it shouldn't be user visible. Calling play()
appears to just do nothing.

   }
 
   /**
@@ -227,6 +238,9 @@ cr.define('hotword', function() {
       // Detector implicitly stops when the hotword is detected.
       this.state_ = State_.STOPPED;
 
+      // Play the chime.
+      this.chime_.play();

[Dan Beam, 2014/09/23 03:43:13]

can this handle being called before the sound stops playing or if not loaded
yet?

[Anand Mistry (off Chromium), 2014/09/24 01:35:02]

The sound is shorter than 1 second. I don't think it's reasonable to try an
handle playing if it's already playing. As for not loaded, the file either
doesn't exist, which should only happen when the shared module isn't installed
and hence this code path won't be invoked, or the URL was slow to be loaded. I'm
not sure if it's worth trying to handle that.

+
       chrome.hotwordPrivate.notifyHotwordRecognition('search', function() {});
 
       // Implicitly clear the session. A session needs to be started in order to