Play a chime when the hotword is triggered.

BUG=397019

Review URL: https://codereview.chromium.org/545373005

Cr-Commit-Position: refs/heads/master@{#296343}

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