Fix issue 2756 where '$' has as special meaning in Javascript String.replace.

tests/corelib/string_replace_dollar_test.dart

Index: tests/corelib/string_replace_dollar_test.dart
===================================================================
--- tests/corelib/string_replace_dollar_test.dart	(revision 0)
+++ tests/corelib/string_replace_dollar_test.dart	(revision 0)
@@ -0,0 +1,17 @@
+// 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.
+
+main() {
+  String jsText = @"""'$'
+""";
+  String htmlStr = '%%DART';
+  String htmlOut = htmlStr.replaceAll("%%DART", jsText);
+  Expect.equals(jsText, htmlOut);
+  htmlOut = htmlStr.replaceFirst("%%DART", jsText);
+  Expect.equals(jsText, htmlOut);
+  htmlOut = htmlStr.replaceAll(new RegExp("%%DART"), jsText);
+  Expect.equals(jsText, htmlOut);
+  htmlOut = htmlStr.replaceFirst(new RegExp("%%DART"), jsText);
+  Expect.equals(jsText, htmlOut);
+}