Move dart2js from sdk/lib/_internal/compiler to pkg/compiler

pkg/compiler/lib/src/mirrors/dart2js_mirrors.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.
 
 library dart2js.mirrors;
 
 import 'dart:collection' show UnmodifiableListView, UnmodifiableMapView;
 
 import '../constants/expressions.dart';
 import '../constants/values.dart';
@@ skipping 481 matching lines @@
   }
 
   static ResolvedNode defaultValueSyntaxOf(Dart2JsParameterMirror parameter) {
     if (!parameter.hasDefaultValue) return null;
     ParameterElement parameterElement = parameter._element;
     var node = parameterElement.initializer;
     var treeElements = parameterElement.treeElements;
     return new ResolvedNode(node, treeElements, parameter.mirrorSystem);
   }
 }