Introduce DeclarationMirror

tests/compiler/dart2js/mirrors_test.dart

 // Copyright (c) 2012, 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.
 
 #import("../../../pkg/dartdoc/lib/mirrors.dart");
 #import("../../../pkg/dartdoc/lib/mirrors_util.dart");
 
 #import('dart:io');
 
 int count(Iterable iterable) {
   var count = 0;
   for (var element in iterable) {
     count++;
   }
   return count;
 }
 
 bool containsType(TypeMirror expected, Iterable<TypeMirror> iterable) {
   for (var element in iterable) {
     if (element.declaration == expected.declaration) {
       return true;
     }
   }
   return false;
 }
 
-Mirror findMirror(List<Mirror> list, String name) {
-  for (Mirror mirror in list) {
+DeclarationMirror findMirror(List<DeclarationMirror> list, String name) {
+  for (DeclarationMirror mirror in list) {
     if (mirror.simpleName == name) {
       return mirror;
     }
   }
   return null;
 }
 
 main() {
   var scriptPath = new Path.fromNative(new Options().script);
   var dirPath = scriptPath.directoryPath;
@@ skipping 693 matching lines @@
   Expect.isTrue(privateConstructor.isConstructor);
   Expect.isTrue(privateConstructor.isPrivate);
 
   var privateFactoryConstructor =
       privateClass.declaredMembers['_PrivateClass._privateFactoryConstructor'];
   Expect.isNotNull(privateFactoryConstructor);
   Expect.isTrue(privateFactoryConstructor is MethodMirror);
   Expect.isTrue(privateFactoryConstructor.isFactory);
   Expect.isTrue(privateFactoryConstructor.isPrivate);
 }