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

pkg/compiler/lib/src/diagnostic_listener.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.
 
 part of dart2js;
 
 abstract class DiagnosticListener {
   // TODO(karlklose): rename log to something like reportInfo.
   void log(message);
 
@@ skipping 16 matching lines @@
 
   void reportInfo(Spannable node, MessageKind errorCode,
                   [Map arguments = const {}]);
 
   // TODO(ahe): We should not expose this here.  Perhaps a
   // [SourceSpan] should implement [Spannable], and we should have a
   // way to construct a [SourceSpan] from a [Spannable] and an
   // [Element].
   withCurrentElement(Element element, f());
 }