Fix equality between subclasses of Source

pkg/analyzer/lib/src/summary/package_bundle_reader.dart

 import 'dart:io' as io;
 
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/context/cache.dart';
 import 'package:analyzer/src/context/context.dart';
 import 'package:analyzer/src/dart/element/element.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/java_io.dart';
 import 'package:analyzer/src/generated/resolver.dart';
 import 'package:analyzer/src/generated/source.dart';
@@ skipping 85 matching lines @@
   @override
   int get modificationStamp => 0;
 
   @override
   String get shortName => pathos.basename(fullName);
 
   @override
   UriKind get uriKind => UriKind.PACKAGE_URI;
 
   @override
-  bool operator ==(Object object) =>
-      object is InSummarySource && object.uri == uri;
+  bool operator ==(Object object) => object is Source && object.uri == uri;
 
   @override
   bool exists() => true;
 
   @override
   String toString() => uri.toString();
 }
 
 /**
  * The [ResultProvider] that provides results using summary resynthesizer.
@@ skipping 229 matching lines @@
  * also provides [summaryPath].
  */
 class _InSummaryFallbackSource extends FileBasedSource
     implements InSummarySource {
   @override
   final String summaryPath;
 
   _InSummaryFallbackSource(JavaFile file, Uri uri, this.summaryPath)
       : super(file, uri);
 }