dart2js: Avoid escaping in strings if it's not necessary.

tests/compiler/dart2js/string_escapes2_test.dart

+// Copyright (c) 2015, 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 'dart:async';
+import 'package:async_helper/async_helper.dart';
+import 'package:expect/expect.dart';
+import 'compiler_helper.dart';
+
+// Test that the compiler doesn't escape too many characters.
+
+Future<String> compileExpression(String expression) {
+  var source = "foo() { return $expression; }";
+  return compile(source, entry: "foo");
+}
+
+Future runTest() {
+  return compileExpression("'Тест на Кирилица - great.\\nNext \"line\".'")

[sra1, 2015/02/17 20:03:53]

Add $PS and $LS.

[floitsch, 2015/02/20 13:55:50]

Done.

+      .then((String generated) {
+    Expect.isTrue(
+        generated.contains(r'"Тест на Кирилица - great.\nNext \"line\"."') ||

[Johnni Winther, 2015/02/17 14:19:46]

Shouldn't it be '\\nNext' instead of '\nNext' ?

[floitsch, 2015/02/20 13:55:50]

No. This string is a raw string.

+        generated.contains("'Тест на Кирилица - great.\\nNext \"line\".'"));
+  });
+}
+
+main() {
+  asyncTest(runTest);
+}