Support basic stereo pan positioning for earcons

chrome/browser/resources/chromeos/chromevox/cvox2/background/next_earcons.js

 // Copyright 2015 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.
 
 /**
  * @fileoverview Earcons library that uses EarconEngine to play back
  * auditory cues.
  */
 
 
@@ skipping 30 matching lines @@
   },
 
   /**
    * @override
    */
   playEarcon: function(earcon) {
     if (!cvox.AbstractEarcons.enabled) {
       return;
     }
     console.log('Earcon ' + earcon);
-
+    if (ChromeVoxState.instance.currentRange &&
+        ChromeVoxState.instance.currentRange.isValid()) {
+      var node = ChromeVoxState.instance.currentRange.start.node;
+      var rect = node.location;

[dmazzoni, 2016/12/05 20:07:45]

Could you use this.locations_ instead, which is computed for the focus ring
calculation? The nice thing about sharing it with that code already calls
boundsForRange and taken the whole range into account, so it will work for an
individual word or a range spanning multiple nodes

[David Tseng, 2016/12/08 19:05:37]

I made it so we're plumbing through rects from the playEarcon call sites. I
don't know if we need word level resolution, so leaving it there at node level
resolution for ranges with multiple nodes.

+      var container = node.root.location;
+      this.engine_.setPositionForRect(rect, container);
+    }
     switch (earcon) {
       case cvox.Earcon.ALERT_MODAL:
       case cvox.Earcon.ALERT_NONMODAL:
         this.engine_.onAlert();
         break;
       case cvox.Earcon.BUTTON:
         this.engine_.onButton();
         break;
       case cvox.Earcon.CHECK_OFF:
         this.engine_.onCheckOff();
@@ skipping 59 matching lines @@
    * @override
    */
   cancelEarcon: function(earcon) {
     switch (earcon) {
       case cvox.Earcon.PAGE_START_LOADING:
         this.engine_.cancelProgress();
         break;
     }
   },
 };