Implement ChromeVox Next menus.

chrome/browser/resources/chromeos/chromevox/common/composite_tts.js

Index: chrome/browser/resources/chromeos/chromevox/common/composite_tts.js
diff --git a/chrome/browser/resources/chromeos/chromevox/common/composite_tts.js b/chrome/browser/resources/chromeos/chromevox/common/composite_tts.js
index 0aa96e3e7e68f9d6e6d2522aa31bb1785f6bd9e1..20cec1dfe6ee29bcf1038375f18140e0a437dc4b 100644
--- a/chrome/browser/resources/chromeos/chromevox/common/composite_tts.js
+++ b/chrome/browser/resources/chromeos/chromevox/common/composite_tts.js
@@ -94,12 +94,23 @@ cvox.CompositeTts.prototype.increaseOrDecreaseProperty =
 /**
  * @override
  */
+cvox.CompositeTts.prototype.propertyToPercentage = function(property) {
+  for (var i = 0, engine; engine = this.ttsEngines_[i]; i++) {
+    var value = engine.propertyToPercentage(property);
+    if (value !== undefined)
+      return value;
+  }
+};
+
+
+/**
+ * @override
+ */
 cvox.CompositeTts.prototype.getDefaultProperty = function(property) {
   for (var i = 0, engine; engine = this.ttsEngines_[i]; i++) {
     var value = engine.getDefaultProperty(property);
-    if (value) {
+    if (value !== undefined)
       return value;
-    }
   }
   return null;
 };