Return virtual braille display size as columns and rows, not text count.

This was causing the braille captions to not show up since change r431444.

BUG=669255
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2532003004
Cr-Commit-Position: refs/heads/master@{#435048}

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

@@ -141,7 +141,9 @@ cvox.BrailleCaptionsBackground.setActive = function(newValue) {
 cvox.BrailleCaptionsBackground.getVirtualDisplayState = function() {
   var self = cvox.BrailleCaptionsBackground;
   if (self.isEnabled()) {
-    return {available: true, textCellCount: 40};  // 40, why not?
+    var rows = parseInt(localStorage['virtualBrailleRows'], 10) || 1;
+    var columns = parseInt(localStorage['virtualBrailleColumns'], 10) || 40;
+    return {available: true, textRowCount: rows, textColumnCount: columns};
   } else {
     return {available: false};
   }