Speed-up 'new TypedArray(arrayLike)'.

src/typedarray.js

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 59 matching lines @@
   function ConstructByLength(obj, length) {
     var l = ToPositiveInteger(length, "invalid_typed_array_length");
     var byteLength = l * elementSize;
     var buffer = new global.ArrayBuffer(byteLength);
     %TypedArrayInitialize(obj, arrayId, buffer, 0, byteLength);
   }
 
   function ConstructByArrayLike(obj, arrayLike) {
     var length = arrayLike.length;
     var l =  ToPositiveInteger(length, "invalid_typed_array_length");
-    var byteLength = l * elementSize;
-    var buffer = new $ArrayBuffer(byteLength);
-    %TypedArrayInitialize(obj, arrayId, buffer, 0, byteLength);
-    for (var i = 0; i < l; i++) {
-      obj[i] = arrayLike[i];
+    if(!%TypedArrayInitializeFromArrayLike(obj, arrayId, arrayLike, l)) {
+      for (var i = 0; i < l; i++) {
+        obj[i] = arrayLike[i];
+      }
     }
   }
 
   return function (arg1, arg2, arg3) {
     if (%_IsConstructCall()) {
       if (IS_ARRAYBUFFER(arg1)) {
         ConstructByArrayBuffer(this, arg1, arg2, arg3);
       } else if (IS_NUMBER(arg1) || IS_STRING(arg1) ||
                  IS_BOOLEAN(arg1) || IS_UNDEFINED(arg1)) {
         ConstructByLength(this, arg1);
@@ skipping 492 matching lines @@
 
       "getFloat32", DataViewGetFloat32,
       "setFloat32", DataViewSetFloat32,
 
       "getFloat64", DataViewGetFloat64,
       "setFloat64", DataViewSetFloat64
   ));
 }
 
 SetupDataView();