More typed array constructors.

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 105 matching lines @@
     %TypedArrayInitialize(obj, arrayId, buffer, offset, newByteLength);
   }
 
   function ConstructByLength(obj, length) {
     var l = IS_UNDEFINED(length) ? 0 : TO_POSITIVE_INTEGER(length);
     var byteLength = l * elementSize;
     var buffer = new $ArrayBuffer(byteLength);
     %TypedArrayInitialize(obj, arrayId, buffer, 0, byteLength);
   }
 
+  function TryConstructByArrayLike(obj, arrayLike) {

[rossberg, 2013/05/02 11:52:20]

Nit: why is this called TryConstruct?

+    var length = arrayLike.length;
+    var l =  IS_UNDEFINED(length) ? 0 : TO_POSITIVE_INTEGER(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];
+    }
+  }
+
   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)) {
+        ConstructByLength(this, arg1);
+      } else if (!IS_UNDEFINED(arg1)){
+        TryConstructByArrayLike(this, arg1);
       } else {
-        ConstructByLength(this, arg1);
+        throw MakeTypeError("parameterless_typed_array_constr", name);
       }
     } else {
       return new constructor(arg1, arg2, arg3);
     }
   }
 }
 
 function TypedArrayGetBuffer() {
   return %TypedArrayGetBuffer(this);
 }
@@ skipping 53 matching lines @@
 // arrayIds below should be synchronized with Runtime_TypedArrayInitialize.
 SetupTypedArray(1, "Uint8Array", global.Uint8Array, 1);
 SetupTypedArray(2, "Int8Array", global.Int8Array, 1);
 SetupTypedArray(3, "Uint16Array", global.Uint16Array, 2);
 SetupTypedArray(4, "Int16Array", global.Int16Array, 2);
 SetupTypedArray(5, "Uint32Array", global.Uint32Array, 4);
 SetupTypedArray(6, "Int32Array", global.Int32Array, 4);
 SetupTypedArray(7, "Float32Array", global.Float32Array, 4);
 SetupTypedArray(8, "Float64Array", global.Float64Array, 8);