Add ChromeVox panel and implement caption display functionality.

chrome/browser/resources/chromeos/chromevox/chromevox/background/braille_captions_background.js

Index: chrome/browser/resources/chromeos/chromevox/chromevox/background/braille_captions_background.js
diff --git a/chrome/browser/resources/chromeos/chromevox/chromevox/background/braille_captions_background.js b/chrome/browser/resources/chromeos/chromevox/chromevox/background/braille_captions_background.js
index 0d2183c970466678700f506f1af19fb32f677b3a..2bbf729cdb68d0b11943e77e54349e7af5f714f7 100644
--- a/chrome/browser/resources/chromeos/chromevox/chromevox/background/braille_captions_background.js
+++ b/chrome/browser/resources/chromeos/chromevox/chromevox/background/braille_captions_background.js
@@ -2,14 +2,16 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-/** @fileoverview Sends braille content to a content script if the braille
- * captions feature is enabled.
+/** @fileoverview If the braille captions feature is enabled, sends
+ * braille content to the Panel on Chrome OS, or a content script on
+ * other platforms.
  */
 
 goog.provide('cvox.BrailleCaptionsBackground');
 
 goog.require('cvox.BrailleDisplayState');
 goog.require('cvox.ExtensionBridge');
+goog.require('cvox.PanelCommand');
 
 /**
  * Key set in local storage when this feature is enabled.
@@ -65,11 +67,19 @@ cvox.BrailleCaptionsBackground.setContent = function(text, cells) {
     brailleChars += String.fromCharCode(
         self.BRAILLE_UNICODE_BLOCK_START | byteBuf[i]);
   }
-  cvox.ExtensionBridge.send({
-    message: 'BRAILLE_CAPTION',
-    text: text,
-    brailleChars: brailleChars
-  });
+
+  if (cvox.ChromeVox.isChromeOS) {
+    (new cvox.PanelCommand(
+        cvox.PanelCommandType.UPDATE_BRAILLE_TEXT, text)).send();
+    (new cvox.PanelCommand(
+        cvox.PanelCommandType.UPDATE_BRAILLE_CELLS, brailleChars)).send();
+  } else {
+    cvox.ExtensionBridge.send({
+      message: 'BRAILLE_CAPTION',
+      text: text,
+      brailleChars: brailleChars
+    });
+  }
 };