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

pkg/compiler/lib/src/js_emitter/old_emitter/class_builder.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.js_emitter;
 
 /**
  * A data structure for collecting fragments of a class definition.
  */
 class ClassBuilder {
@@ skipping 42 matching lines @@
           new jsAst.ArrayInitializer.from([classData]..addAll(fieldMetadata));
     }
     var fieldsAndProperties =
         [new jsAst.Property(js.string(namer.classDescriptorProperty),
                             classData)]
         ..addAll(properties);
     return new jsAst.ObjectInitializer(fieldsAndProperties, isOneLiner: false);
   }
 
 }