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

tests/lib/mirrors/typevariable_mirror_metadata_test.dart

Index: tests/lib/mirrors/typevariable_mirror_metadata_test.dart
diff --git a/tests/lib/mirrors/typevariable_mirror_metadata_test.dart b/tests/lib/mirrors/typevariable_mirror_metadata_test.dart
index 9994988fc67c0bc7902c6b3b742d2e8314770890..aa59870a9ba375c9cff5dfc880ef086b712e5e87 100644
--- a/tests/lib/mirrors/typevariable_mirror_metadata_test.dart
+++ b/tests/lib/mirrors/typevariable_mirror_metadata_test.dart
@@ -9,7 +9,7 @@ import "dart:mirrors";
 import "metadata_test.dart";
 
 const m1 = 'm1';
-const m2 = const Symbol('m2');
+const m2 = #m2;
 const m3 = 3;
 
 class A <S, @m1 @m2 T> {
@@ -35,12 +35,12 @@ main() {
   checkMetadata(cm.typeVariables[0], []);
   checkMetadata(cm.typeVariables[1], [m1, m2]);
   // Check for conflicts.
-  checkMetadata(cm.methods[const Symbol('T')], [m3]);
+  checkMetadata(cm.methods[#T], [m3]);
 
   cm = reflectClass(B);
   checkMetadata(cm.typeVariables[0], [m3]);
   // Check for conflicts.
-  checkMetadata(cm.members[const Symbol('T')], [m1, m2]);
+  checkMetadata(cm.members[#T], [m1, m2]);
 
   TypedefMirror tm = reflectClass(Predicate);
   FunctionTypeMirror ftm = tm.referent;