Convert raw strings to new syntax

tests/corelib/reg_exp4_test.dart

Index: tests/corelib/reg_exp4_test.dart
===================================================================
--- tests/corelib/reg_exp4_test.dart	(revision 12867)
+++ tests/corelib/reg_exp4_test.dart	(working copy)
@@ -13,7 +13,7 @@
     }
   }
   try {
-    const RegExp(@"^\w+$").hasMatch(null);
+    const RegExp(r"^\w+$").hasMatch(null);
     Expect.fail("Expected: NullPointerException got: no exception");
   } on Exception catch (ex) {
     if (!(ex is NullPointerException)) {
@@ -21,7 +21,7 @@
     }
   }
   try {
-    const RegExp(@"^\w+$").firstMatch(null);
+    const RegExp(r"^\w+$").firstMatch(null);
     Expect.fail("Expected: NullPointerException got: no exception");
   } on Exception catch (ex) {
     if (!(ex is NullPointerException)) {
@@ -29,7 +29,7 @@
     }
   }
   try {
-    const RegExp(@"^\w+$").allMatches(null);
+    const RegExp(r"^\w+$").allMatches(null);
     Expect.fail("Expected: NullPointerException got: no exception");
   } on Exception catch (ex) {
     if (!(ex is NullPointerException)) {
@@ -37,7 +37,7 @@
     }
   }
   try {
-    const RegExp(@"^\w+$").stringMatch(null);
+    const RegExp(r"^\w+$").stringMatch(null);
     Expect.fail("Expected: NullPointerException got: no exception");
   } on Exception catch (ex) {
     if (!(ex is NullPointerException)) {