Factor out core of Array.forEach and .every, for use in TypedArrays

test/mjsunit/harmony/typedarrays-foreach.js

Index: test/mjsunit/harmony/typedarrays-foreach.js
diff --git a/test/mjsunit/harmony/typedarrays-foreach.js b/test/mjsunit/harmony/typedarrays-foreach.js
index 4bfa655449363e50e6817fe0fb38bc3656035a71..0d34c78efb20f87ddd016c509d8a65dd5aecf592 100644
--- a/test/mjsunit/harmony/typedarrays-foreach.js
+++ b/test/mjsunit/harmony/typedarrays-foreach.js
@@ -85,8 +85,13 @@ function TestTypedArrayForEach(constructor) {
   assertEquals(42, a[1]);
 
   // Neutering the buffer backing the typed array mid-way should
-  // still make .forEach() finish, and the array should keep being
-  // empty after neutering it.
+  // still make .forEach() finish, but exiting early due to the missing
+  // elements, and the array should keep being empty after detaching it.
+  // TODO(dehrenberg): According to the ES6 spec, accessing or testing
+  // for members on a detached TypedArray should throw, so really this
+  // should throw in the third iteration. However, this behavior matches
+  // the Khronos spec.
+  a = new constructor(3);
   count = 0;
   a.forEach(function (n, index, array) {
     if (count > 0) %ArrayBufferNeuter(array.buffer);