rename completion source files to match content

pkg/analysis_server/lib/src/services/completion/combinator_contributor.dart

 // Copyright (c) 2014, 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 services.completion.contributor.dart.combinator;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/protocol_server.dart'
     hide Element, ElementKind;
@@ skipping 62 matching lines @@
     var directive = node.getAncestor((parent) => parent is NamespaceDirective);
     if (directive is NamespaceDirective) {
       LibraryElement library = directive.uriElement;
       if (library != null) {
         library.visitChildren(this);
       }
     }
     return new Future.value(false);
   }
 }