Use an enum for ChromeVox queue mode.

chrome/browser/resources/chromeos/chromevox/chromevox/injected/api_implementation.js

Index: chrome/browser/resources/chromeos/chromevox/chromevox/injected/api_implementation.js
diff --git a/chrome/browser/resources/chromeos/chromevox/chromevox/injected/api_implementation.js b/chrome/browser/resources/chromeos/chromevox/chromevox/injected/api_implementation.js
index eee5db6f81ebd13fe54fc6b7e834780bad387763..0db02e9e250576973ee7771a2e40fd9dc29d1bfb 100644
--- a/chrome/browser/resources/chromeos/chromevox/chromevox/injected/api_implementation.js
+++ b/chrome/browser/resources/chromeos/chromevox/chromevox/injected/api_implementation.js
@@ -143,7 +143,9 @@ cvox.ApiImplementation.speak = function(
       properties = {};
     }
     setupEndCallback_(properties, callbackId);
-    cvox.ChromeVox.tts.speak(textString, queueMode, properties);
+    cvox.ChromeVox.tts.speak(textString,
+                             /** @type {cvox.QueueMode} */ (queueMode),
+                             properties);
   }
 };
 
@@ -158,7 +160,7 @@ cvox.ApiImplementation.speakNode = function(node, queueMode, properties) {
   if (cvox.ChromeVox.isActive) {
     cvox.ChromeVox.tts.speak(
         cvox.DomUtil.getName(node),
-        queueMode,
+        /** @type {cvox.QueueMode} */ (queueMode),
         properties);
   }
 };
@@ -261,7 +263,7 @@ cvox.ApiImplementation.syncToNode = function(
   }
 
   if (opt_queueMode == undefined) {
-    opt_queueMode = cvox.AbstractTts.QUEUE_MODE_CATEGORY_FLUSH;
+    opt_queueMode = cvox.QueueMode.CATEGORY_FLUSH;
   }
 
   cvox.ChromeVox.navigationManager.updateSelToArbitraryNode(targetNode, true);
@@ -279,7 +281,7 @@ cvox.ApiImplementation.syncToNode = function(
   if (opt_speakNode) {
     cvox.ChromeVox.navigationManager.speakDescriptionArray(
         cvox.ApiImplementation.getDesc_(targetNode),
-        opt_queueMode,
+        /** @type {cvox.QueueMode} */ (opt_queueMode),
         null,
         null,
         cvox.TtsCategory.NAV);