Fix support for uri in part-of directive

pkg/analyzer/lib/src/dart/ast/ast.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 analyzer.src.dart.ast.ast;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/syntactic_entity.dart';
@@ skipping 8440 matching lines @@
       this.semicolon)
       : super(comment, metadata) {
     _uri = _becomeParentOf(uri);
     _libraryName = _becomeParentOf(libraryName);
   }
 
   @override
   Iterable<SyntacticEntity> get childEntities => super._childEntities
     ..add(partKeyword)
     ..add(ofKeyword)
+    ..add(_uri)
     ..add(_libraryName)
     ..add(semicolon);
 
   @override
   Token get endToken => semicolon;
 
   @override
   Token get firstTokenAfterCommentAndMetadata => partKeyword;
 
   @override
@@ skipping 3013 matching lines @@
 
   @override
   dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
       visitor.visitYieldStatement(this);
 
   @override
   void visitChildren(AstVisitor visitor) {
     _expression?.accept(visitor);
   }
 }