Fix bad call of RangeError.value in String.fromCharCodes.

tests/corelib/string_fromcharcodes_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import "package:expect/expect.dart";
 import "dart:typed_data";
 
 main() {
   iter(count, [values]) => values is List
                                ? new Iterable.generate(count, (x) => values[x])
@@ skipping 131 matching lines @@
     test("AB", iterable, 0, 2);
     test("GH", iterable, 6, 8);
     test("DE", iterable, 3, 5);
     test("", iterable, 3, 3);
   }
   // Can split surrogates in input, but not a single big code point.
   test(leadSurrogate, [0xDBFF, 0xDFFF], 0, 1);
   test(tailSurrogate, [0xDBFF, 0xDFFF], 1);
   test("\u{10FFFF}", [0x10FFFF], 0, 1);
 
+  void testThrowsRange(iterable, [start = 0, end]) {
+    Expect.throws(() => new String.fromCharCodes(iterable, start, end),
+                  (e) => e is RangeError);
+  }
+
   // Test varying slices of the code units of a string.
   testSubstring(string) {
     var codes = string.codeUnits;
     int length = string.length;
     for (var iterable in [
             iter(length, codes),
             codes.toList(growable: true),
             codes.toList(growable: false),
             new Uint16List(length)..setRange(0, length, codes),
             new Int32List(length)..setRange(0, length, codes),
             new Uint32List(length)..setRange(0, length, codes),
             codes,
         ]) {
       var newString = new String.fromCharCodes(iterable);
       Expect.equals(string, newString);
       for (int i = 0; i < length; i = i * 2 + 1) {
         test(string.substring(i), iterable, i);
         test(string.substring(0, i), iterable, 0, i);
         for (int j = 0; i + j < length; j = j * 2 + 1) {
           test(string.substring(i, i + j), iterable, i, i + j);
         }
       }
 
-      Expect.throws(() => new String.fromCharCodes(iterable, -1));
-      Expect.throws(() => new String.fromCharCodes(iterable, 0, -1));
-      Expect.throws(() => new String.fromCharCodes(iterable, 2, 1));
-      Expect.throws(() => new String.fromCharCodes(iterable, 0, length + 1));
-      Expect.throws(() => new String.fromCharCodes(iterable, length + 1));
-      Expect.throws(() => new String.fromCharCodes(iterable, length + 1,
-                                                             length + 2));
+      testThrowsRange(iterable, -1);
+      testThrowsRange(iterable, 0, -1);
+      testThrowsRange(iterable, 2, 1);
+      testThrowsRange(iterable, 0, length + 1);
+      testThrowsRange(iterable, length + 1);
+      testThrowsRange(iterable, length + 1, length + 2);
     }
   }
 
   testSubstring("");
   testSubstring("ABCDEFGH");
   // length > 128
   testSubstring("ABCDEFGH" * 33);
   testSubstring("\x00" * 357);
   // length > 128 and non-ASCII.
   testSubstring("\uFFFD\uFFFE\u{10000}\u{10ffff}c\x00" * 37);
 }