Fixed use of undefined in ArraySort.

Changed 'undefined' in ArraySort to 'void 0'. Also added regression test to catch the error.
Review URL: http://codereview.chromium.org/6073

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@406 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/array.js

@@ -743,7 +743,7 @@ function ArraySort(comparefn) {
     if (IS_UNDEFINED(this[i])) {
       length--;
       this[i] = this[length];
-      this[length] = undefined;
+      this[length] = void 0;
     } else {
       i++;
     }

test/mjsunit/array-sort.js

@@ -131,3 +131,12 @@ function TestArraySortingWithHoles() {
 }
 
 TestArraySortingWithHoles();
+
+// Test array sorting with undefined elemeents in the array.
+function TestArraySortingWithUndefined() {
+  var a = [3, void 0, 2];
+  a.sort();
+  assertArrayEquals([ 2, 3, void 0], a);
+}
+
+TestArraySortingWithUndefined();