Use symbol literals in the mirror tests. (Except for void, the empty string and setters.)

tests/lib/mirrors/mirrors_resolve_fields_test.dart

Index: tests/lib/mirrors/mirrors_resolve_fields_test.dart
diff --git a/tests/lib/mirrors/mirrors_resolve_fields_test.dart b/tests/lib/mirrors/mirrors_resolve_fields_test.dart
index f513ae22ed208287afaaef2e4b0481dfeef19f0f..cb3044f81726f501fe47f9dcfe82c9b8c5dc367f 100644
--- a/tests/lib/mirrors/mirrors_resolve_fields_test.dart
+++ b/tests/lib/mirrors/mirrors_resolve_fields_test.dart
@@ -17,6 +17,6 @@ class A {
 main() {
   var mirrors = currentMirrorSystem();  
   var classMirror = reflectClass(A);
-  var instanceMirror = classMirror.newInstance(const Symbol(''),[]);
+  var instanceMirror = classMirror.newInstance(const Symbol(''), []);
   Expect.equals(A._STATE_INITIAL, instanceMirror.reflectee._state);
 }