Handle escapes in string literals.

frog/tests/leg/src/StringEscapesTest.dart

+// Copyright (c) 2011, 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("compiler_helper.dart");
+
+// Test that the compiler handles string literals containing line terminators.
+
+final String TEST_ONE = """
+foo() {
+  return '''\n\r\u2028\u2029''';
+}
+""";
+
+final String TEST_TWO = """
+foo() {
+  return @'''\n\r\u2028\u2029''';
+}
+""";
+
+final String TEST_THREE = """
+foo() {
+  return '\u2028\u2029';
+}
+""";
+
+main() {
+  String generated = compile(TEST_ONE, 'foo');
+  print(generated);
+  Expect.isTrue(generated.contains(@"\n\r\u2028\u2029"));
+
+  generated = compile(TEST_TWO, 'foo');
+  Expect.isTrue(generated.contains(@"\n\r\u2028\u2029"));
+
+  generated = compile(TEST_THREE, 'foo');
+  Expect.isTrue(generated.contains(@"\u2028\u2029"));
+}