Move dart2jslib parts into separate libraries.

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;
+library dart2js.diagnostic_listener;
+
+import 'dart2jslib.dart' show
+    SourceSpan;
+import 'elements/elements.dart' show
+    Element;
+import 'messages.dart';
+import 'util/util.dart' show
+    Spannable;
 
 abstract class DiagnosticListener {
   // TODO(karlklose): rename log to something like reportInfo.
   void log(message);
 
   void internalError(Spannable spannable, message);
 
   SourceSpan spanFromSpannable(Spannable node);
 
   void reportError(Spannable node, MessageKind errorCode,
                    [Map arguments = const {}]);
 
   void reportWarning(Spannable node, MessageKind errorCode,
                      [Map arguments = const {}]);
 
   void reportHint(Spannable node, MessageKind errorCode,
                   [Map arguments = const {}]);
 
   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());
 }