Support basic stereo pan positioning for earcons

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

Index: chrome/browser/resources/chromeos/chromevox/cvox2/background/next_earcons.js
diff --git a/chrome/browser/resources/chromeos/chromevox/cvox2/background/next_earcons.js b/chrome/browser/resources/chromeos/chromevox/cvox2/background/next_earcons.js
index 9d2a6b4b25fc13bdea8fb336afe8d4e68072ba32..1c9e5cd6b18c691fc7339e0a190ff53153caab59 100644
--- a/chrome/browser/resources/chromeos/chromevox/cvox2/background/next_earcons.js
+++ b/chrome/browser/resources/chromeos/chromevox/cvox2/background/next_earcons.js
@@ -48,7 +48,13 @@ NextEarcons.prototype = {
       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: