Fix Unicode issues in dart2js and dart2dart.

tests/utils/uri_test.dart

Index: tests/utils/uri_test.dart
diff --git a/tests/utils/uri_test.dart b/tests/utils/uri_test.dart
index 7acc5cff1df6b3feb967970d37c61284d3ac72bc..66820dc1f72c0171809bad7bf58ce0848dd39842 100644
--- a/tests/utils/uri_test.dart
+++ b/tests/utils/uri_test.dart
@@ -187,10 +187,11 @@ main() {
       "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");