issue 4817 fixed. Implemented raw strings with 'r' instead of '@' for dart2js

tests/compiler/dart2js/builtin_interceptor_test.dart

Index: tests/compiler/dart2js/builtin_interceptor_test.dart
diff --git a/tests/compiler/dart2js/builtin_interceptor_test.dart b/tests/compiler/dart2js/builtin_interceptor_test.dart
index 229a9d6f0e730b839c258d80586f4066ee120c9a..b904a59d009f01fdce11b4c7f85c266e2b95feb3 100644
--- a/tests/compiler/dart2js/builtin_interceptor_test.dart
+++ b/tests/compiler/dart2js/builtin_interceptor_test.dart
@@ -4,7 +4,7 @@
 
 #import("compiler_helper.dart");
 
-const String TEST_ONE = @"""
+const String TEST_ONE = r"""
 foo(String a) {
   // index into the parameter and move into a loop to make sure we'll get a
   // type guard.
@@ -15,19 +15,19 @@ foo(String a) {
 }
 """;
 
-const String TEST_TWO = @"""
+const String TEST_TWO = r"""
 foo() {
   return "foo".length;
 }
 """;
 
-const String TEST_THREE = @"""
+const String TEST_THREE = r"""
 foo() {
-  return @"foo".length;
+  return r"foo".length;
 }
 """;
 
-const String TEST_FOUR = @"""
+const String TEST_FOUR = r"""
 foo() {
   return new List().add(2);
 }