Fix Unicode issues in dart2js and dart2dart.

tests/utils/uri_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.
 
 library uriTest;
 
 import 'dart:utf';
 import 'dart:uri';
 
 testUri(String uri, bool isAbsolute) {
@@ skipping 169 matching lines @@
   Expect.throws(
       () => new Uri.fromString("http://:80").origin,
       (e) { return e is ArgumentError; },
       "origin for uri with empty domain should fail");
   Expect.throws(
       () => new Uri.fromString("file://localhost/test.txt").origin,
       (e) { return e is ArgumentError; },
       "origin for non-http/https uri should fail");
 
   // URI encode tests
-  // Note: dart2js won't handle '\ud800\udc00' and frog
-  // won't handle '\u{10000}'. So we cons this up synthetically...
+  // Create a string with code point 0x10000 encoded as a surrogate pair.
   var s = decodeUtf8([0xf0, 0x90, 0x80, 0x80]);
 
+  Expect.stringEquals("\u{10000}", s);
+
   testEncodeDecode("\uFFFE", "%EF%BF%BE");
   testEncodeDecode("\uFFFF", "%EF%BF%BF");
   testEncodeDecode("\uFFFE", "%EF%BF%BE");
   testEncodeDecode("\uFFFF", "%EF%BF%BF");
   testEncodeDecode("\x7f", "%7F");
   testEncodeDecode("\x80", "%C2%80");
   testEncodeDecode("\u0800", "%E0%A0%80");
   testEncodeDecode(":/@',;?&=+\$", ":/@',;?&=+\$");
   testEncodeDecode(s, "%F0%90%80%80");
   testEncodeDecodeComponent("\uFFFE", "%EF%BF%BE");
   testEncodeDecodeComponent("\uFFFF", "%EF%BF%BF");
   testEncodeDecodeComponent("\uFFFE", "%EF%BF%BE");
   testEncodeDecodeComponent("\uFFFF", "%EF%BF%BF");
   testEncodeDecodeComponent("\x7f", "%7F");
   testEncodeDecodeComponent("\x80", "%C2%80");
   testEncodeDecodeComponent("\u0800", "%E0%A0%80");
   testEncodeDecodeComponent(":/@',;?&=+\$", "%3A%2F%40'%2C%3B%3F%26%3D%2B%24");
   testEncodeDecodeComponent(s, "%F0%90%80%80");
 }