cr.js: Replace usage of ES6 Map with Object.

ui/webui/resources/js/cr.js

Index: ui/webui/resources/js/cr.js
diff --git a/ui/webui/resources/js/cr.js b/ui/webui/resources/js/cr.js
index ceb1eb9707474fb9d91f9bc6b12ad5b13858569f..535c85a310948cc67d047b8ca4098b554ce3582a 100644
--- a/ui/webui/resources/js/cr.js
+++ b/ui/webui/resources/js/cr.js
@@ -320,7 +320,7 @@ var cr = function() {
    * is unique across all invocations of said method.
    * @type {!Map<string, Function>}

[Dan Beam, 2015/07/09 21:03:27]

^ fix

[James Hawkins, 2015/07/09 22:02:50]

Done.

    */
-  var chromeSendCallbackMap = new Map();
+  var chromeSendCallbackMap = Object.create(null);
 
   /**
    * The named method the WebUI handler calls directly in response to a
@@ -335,9 +335,9 @@ var cr = function() {
    *    response is tied to.
    */
   function webUIResponse(id) {
-    chromeSendCallbackMap.get(id).apply(
+    chromeSendCallbackMap[id].apply(
         null, Array.prototype.slice.call(arguments, 1));
-    chromeSendCallbackMap.delete(id);
+    delete chromeSendCallbackMap[id];
   }
 
   /**
@@ -353,7 +353,7 @@ var cr = function() {
    */
   function sendWithCallback(methodName, args, callback) {
     var id = methodName + createUid();
-    chromeSendCallbackMap.set(id, callback);
+    chromeSendCallbackMap[id] = callback;
     chrome.send(methodName, ['cr.webUIResponse', id].concat(args || []));
   }
 
@@ -362,7 +362,7 @@ var cr = function() {
    * register listeners.
    * @type {!Map<string, Array<Function>>}
    */
-  var webUIListenerMap = new Map();
+  var webUIListenerMap = Object.create(null);
 
   /**
    * The named method the WebUI handler calls directly when an event occurs.
@@ -372,7 +372,7 @@ var cr = function() {
    * @param {string} event The name of the event that has occurred.
    */
   function webUIListenerCallback(event) {
-    var listenerCallbacks = webUIListenerMap.get(event);
+    var listenerCallbacks = webUIListenerMap[event];
     for (var i = 0; i < listenerCallbacks.length; i++) {

[Dan Beam, 2015/07/09 21:03:27]

wait, this doesn't make much sense...

chrome.send('name', argsThatTakeLonger, callbackForFirstArgs);
chrome.send('name', differentArgsThatFinishSooner, callbackForSecondArgs);

are both executed when the first 'name' callback returns?  with the same result?

[James Hawkins, 2015/07/09 22:02:50]

The code you're commenting is the event listener code, which is different from
the chrome.send w/ callback code (above).  Is that intentional?

[Dan Beam, 2015/07/09 22:11:15]

ah, no.

btw, i just saw the createUid() that handles this in sendWithCallback()

       var callback = listenerCallbacks[i];
       callback.apply(null, Array.prototype.slice.call(arguments, 1));
@@ -386,10 +386,10 @@ var cr = function() {
    * @param {Function} callback The callback run when the event is fired.
    */
   function addWebUIListener(event, callback) {
-    if (!webUIListenerMap.has(event))
-      webUIListenerMap.set(event, [callback]);
+    if (event in webUIListenerMap)
+      webUIListenerMap[event].push(callback);
     else
-      webUIListenerMap.get(event).push(callback);
+      webUIListenerMap[event] = [callback];
   }
 
   return {