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

pkg/compiler/lib/src/mirrors/dart2js_instance_mirrors.dart

 // Copyright (c) 2013, 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.
 
 part of dart2js.mirrors;
 
 abstract class ObjectMirrorMixin implements ObjectMirror {
   InstanceMirror getField(Symbol fieldName) {
     throw new UnsupportedError('ObjectMirror.getField unsupported.');
   }
@@ skipping 282 matching lines @@
       return new Dart2JsBoolConstantMirror.fromBool(mirrorSystem, isDocComment);
     } else if (fieldName == #text) {
       return new Dart2JsStringConstantMirror.fromString(mirrorSystem, text);
     } else if (fieldName == #trimmedText) {
       return new Dart2JsStringConstantMirror.fromString(mirrorSystem,
                                                         trimmedText);
     }
     return super.getField(fieldName);
   }
 }