Check const map literal keys and switch case exprs using type of constant.

tests/language/switch_case_static_const_test.dart

 // Copyright (c) 2014, 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.
 
 class A {
-  static var a;
-  var b;
+  static const S = 'A.S';
 }
 
-class B extends A {
+const S = 'S';
 
+foo(var p) {
+  switch (p) {
+    case S:
+      break;
+    case A.S:
+      break;
+    case 'abc':
+      break;
+  }
 }
 
-class C extends B {
-  var a; /// 01: static type warning
-  static var b; /// 02: compile-time error
+main() {
+  foo('p');
 }
-
-void main() {
-  new C();
-}