Use an enum for ChromeVox queue mode.

chrome/browser/resources/chromeos/chromevox/host/interface/tts_interface.js

 // Copyright 2014 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 Defines a Tts interface.
  *
  * All TTS engines in ChromeVox conform to the this interface.
  *
  */
 
+goog.provide('cvox.QueueMode');
 goog.provide('cvox.TtsCapturingEventListener');
 goog.provide('cvox.TtsCategory');
 goog.provide('cvox.TtsInterface');
 
 /**
  * Categories for a speech utterance. This can be used with the
  * CATEGORY_FLUSH queue mode, which flushes all utterances from a given
  * category but not other utterances.
  *
  * NAV: speech related to explicit navigation, or focus changing.
+ * LIVE: speech coming from changes to live regions.
  *
  * @enum {string}
  */
 cvox.TtsCategory = {
   LIVE: 'live',
   NAV: 'nav'
 };
 
 /**
+ * Queue modes for calls to {@code cvox.TtsInterface.speak}.
+ * @enum
+ */
+cvox.QueueMode = {
+  /** Stop speech, clear everything, then speak this utterance. */
+  FLUSH: 0,
+
+  /** Append this utterance to the end of the queue. */
+  QUEUE: 1,
+
+  /**
+   * Clear any utterances of the same category (as set by
+   * properties['category']) from the queue, then enqueue this utterance.
+   */
+  CATEGORY_FLUSH: 2
+};
+
+/**
  * @interface
  * An interface for clients who want to get notified when an utterance
  * starts or ends from any source.
  */
 cvox.TtsCapturingEventListener = function() { };
 
 /**
  * Called when any utterance starts.
  */
 cvox.TtsCapturingEventListener.prototype.onTtsStart = function() { };
 
 /**
  * Called when any utterance ends.
  */
 cvox.TtsCapturingEventListener.prototype.onTtsEnd = function() { };
 
 
 /**
  * @interface
  */
 cvox.TtsInterface = function() { };
 
 /**
  * Speaks the given string using the specified queueMode and properties.
  * @param {string} textString The string of text to be spoken.
- * @param {number=} queueMode The queue mode: cvox.AbstractTts.QUEUE_MODE_FLUSH
- *        for flush, cvox.AbstractTts.QUEUE_MODE_QUEUE for adding to queue.
+ * @param {cvox.QueueMode} queueMode The queue mode to use for speaking.
  * @param {Object=} properties Speech properties to use for this utterance.
  * @return {cvox.TtsInterface} A tts object useful for chaining speak calls.
  */
 cvox.TtsInterface.prototype.speak =
     function(textString, queueMode, properties) { };
 
 
 /**
  * Returns true if the TTS is currently speaking.
  * @return {boolean} True if the TTS is speaking.
@@ skipping 21 matching lines @@
 cvox.TtsInterface.prototype.increaseOrDecreaseProperty =
     function(propertyName, increase) { };
 
 
 /**
  * Returns the default properties of the first tts that has default properties.
  * @param {string} property Name of property.
  * @return {?number} The default value.
  */
 cvox.TtsInterface.prototype.getDefaultProperty = function(property) { };