Remove deprecated string features.

tests/corelib/string_codeunits_test.dart

Index: tests/corelib/string_codeunits_test.dart
diff --git a/tests/corelib/string_codeunits_test.dart b/tests/corelib/string_codeunits_test.dart
index 81625c5d186c3bd1787ff71a3401ef89bd44191e..6e3a282a3ae20b12d11c780f3917a967a7d78dc4 100644
--- a/tests/corelib/string_codeunits_test.dart
+++ b/tests/corelib/string_codeunits_test.dart
@@ -31,11 +31,14 @@ main() {
   test("\x00\u0000\u{000000}");
   test("\u{ffff}\u{10000}\u{10ffff}");
   String string = new String.fromCharCodes(
-      [0xdc00, 0xd800, 61, 0xd800, 0xdc00, 62, 0xdc00, 0xd800]);
+      [0xdc00, 0xd800, 61, 0xd9ab, 0xd9ab, 0xddef, 0xddef, 62, 0xdc00, 0xd800]);
+  test(string);
+  string = "\x00\x7f\xff\u0100\ufeff\uffef\uffff"
+           "\u{10000}\u{12345}\u{1d800}\u{1dc00}\u{1ffef}\u{1ffff}";
   test(string);
 
-  // Setting position in the middle of a surrogate pair is not allowed.
-  var r = new CodeUnits("\u{10000}");
+  // Reading each unit of a surrogate pair works.
+  var r = "\u{10000}".codeUnits;
   var it = r.iterator;
   Expect.isTrue(it.moveNext());
   Expect.equals(0xD800, it.current);