Remove _LibraryNode altogether.

pkg/analyzer/lib/src/dart/analysis/file_state.dart

 // Copyright (c) 2016, 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.
 
 import 'dart:convert';
 import 'dart:typed_data';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/error/listener.dart';
@@ skipping 191 matching lines @@
       _transitiveSignature = signature.toHex();
     }
     return _transitiveSignature;
   }
 
   /**
    * The [UnlinkedUnit] of the file.
    */
   UnlinkedUnit get unlinked => _unlinked;
 
+  /**
+   * Return the [uri] string.
+   */
+  String get uriStr => uri.toString();
+
   @override
   bool operator ==(Object other) {
     return other is FileState && other.uri == uri;
   }
 
   /**
    * Return a new parsed unresolved [CompilationUnit].
    */
   CompilationUnit parse(AnalysisErrorListener errorListener) {
     AnalysisOptions analysisOptions = _fsState._analysisOptions;
@@ skipping 328 matching lines @@
         .where((f) => f._transitiveFiles == null)
         .toSet();
   }
 
   Set<FileState> get filesWithoutTransitiveSignature {
     return state._uriToFile.values
         .where((f) => f._transitiveSignature == null)
         .toSet();
   }
 }