Replace ToAsciiVector and ToUC16Vector with single function that returns a tagged value.

test/mjsunit/string-split.js

 // Copyright 2008 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 98 matching lines @@
 assertEquals([], "abc".split("", 0));
 assertEquals([], "abc".split("", numberObj(0)));
 assertEquals(["a"], "abc".split("", 1));
 assertEquals(["a"], "abc".split("", numberObj(1)));
 assertEquals(["a", "b"], "abc".split("", 2));
 assertEquals(["a", "b"], "abc".split("", numberObj(2)));
 assertEquals(["a", "b", "c"], "abc".split("", 3));
 assertEquals(["a", "b", "c"], "abc".split("", numberObj(3)));
 assertEquals(["a", "b", "c"], "abc".split("", 4));
 assertEquals(["a", "b", "c"], "abc".split("", numberObj(4)));
+
+var all_ascii_chars = [];
+for (var i = 0; i < 128; i++) all_ascii_chars[i] = String.fromCharCode(i);
+var all_ascii_string = all_ascii_chars.join("");
+
+var split_chars = all_ascii_string.split("");
+assertEquals(128, split_chars.length);
+for (var i = 0; i < 128; i++) {
+  assertEquals(1, split_chars[i].length);
+  assertEquals(i, split_chars[i].charCodeAt(0));
+}