Remove 2-arg createBuffer from WebAudio

LayoutTests/webaudio/resources/buffer-loader.js

 function BufferLoader(context, urlList, callback) {
     this.context = context;
     this.urlList = urlList;
     this.onload = callback;
     this.bufferList = new Array();
     this.loadCount = 0;
 }
 
 BufferLoader.prototype.loadBuffer = function(url, index) {
     // Load buffer asynchronously
     var request = new XMLHttpRequest();
     request.open("GET", url, true);
     request.responseType = "arraybuffer";
 
     var loader = this;
 
     request.onload = function() {
-        var buffer;
-        try {
-            buffer = loader.context.createBuffer(request.response, false);
-        } catch(e) {
-            alert('error decoding file data: ' + url);
-        }
-
-        try {
-            loader.bufferList[index] = buffer;
-            if (++loader.loadCount == loader.urlList.length)
-                loader.onload(loader.bufferList);
-        } catch(e) {
-            alert('BufferLoader: callback problem');
-        }
+        loader.context.decodeAudioData(
+            request.response,
+            function (decodedAudio) {
+                try {
+                    loader.bufferList[index] = decodedAudio;
+                    if (++loader.loadCount == loader.urlList.length)
+                        loader.onload(loader.bufferList);
+                } catch(e) {
+                    alert('BufferLoader: unable to load buffer' + index);
+                }
+            },
+            function () {
+                alert('error decoding file data: ' + url);
+            });
     }
 
     request.onerror = function() {
         alert('BufferLoader: XHR error');        
     }
 
     request.send();
 }
 
 BufferLoader.prototype.load = function() {
     for (var i = 0; i < this.urlList.length; ++i)
         this.loadBuffer(this.urlList[i], i);
 }