Fix for subscribing for notifications for files in packages.

pkg/analyzer/lib/file_system/memory_file_system.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 memory_file_system;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/src/generated/engine.dart' show TimestampedData;
@@ skipping 234 matching lines @@
   @override
   bool isOrContains(String path) {
     return path == this.path;
   }
 }
 
 /**
  * An in-memory implementation of [Source].
  */
 class _MemoryFileSource extends Source {
-  final _MemoryFile _file;
+  /**
+   * Map from encoded URI/filepath pair to a unique integer identifier.  This
+   * identifier is used for equality tests and hash codes.
+   *
+   * The URI and filepath are joined into a pair by separating them with an '@'
+   * character.
+   */
+  static final Map<String, int> _idTable = new HashMap<String, int>();
+
+  final _MemoryFile file;
 
   final Uri uri;
 
-  _MemoryFileSource(this._file, this.uri);
+  /**
+   * The unique ID associated with this [_MemoryFileSource].
+   */
+  final int id;
+
+  _MemoryFileSource(_MemoryFile file, Uri uri)
+      : uri = uri,
+        file = file,
+        id = _idTable.putIfAbsent('$uri@${file.path}', () => _idTable.length);
 
   @override
   TimestampedData<String> get contents {
-    return new TimestampedData<String>(modificationStamp, _file._content);
+    return new TimestampedData<String>(modificationStamp, file._content);
   }
 
   @override
   String get encoding {
     return uri.toString();
   }
 
   @override
-  String get fullName => _file.path;
+  String get fullName => file.path;
 
   @override
-  int get hashCode => _file.hashCode;
+  int get hashCode => id;
 
   @override
   bool get isInSystemLibrary => uriKind == UriKind.DART_URI;
 
   @override
   int get modificationStamp {
     try {
-      return _file.modificationStamp;
+      return file.modificationStamp;
     } on FileSystemException catch (e) {
       return -1;
     }
   }
 
   @override
-  String get shortName => _file.shortName;
+  String get shortName => file.shortName;
 
   @override
   UriKind get uriKind {
     String scheme = uri.scheme;
     if (scheme == PackageUriResolver.PACKAGE_SCHEME) {
       return UriKind.PACKAGE_URI;
     } else if (scheme == DartUriResolver.DART_SCHEME) {
       return UriKind.DART_URI;
     } else if (scheme == FileUriResolver.FILE_SCHEME) {
       return UriKind.FILE_URI;
     }
     return UriKind.FILE_URI;
   }
 
   @override
   bool operator ==(other) {
-    if (other is _MemoryFileSource) {
-      return other._file == _file;
-    }
-    return false;
+    return other is _MemoryFileSource && other.id == id;
   }
 
   @override
-  bool exists() => _file.exists;
+  bool exists() => file.exists;
 
   @override
   Uri resolveRelativeUri(Uri relativeUri) {
     return uri.resolveUri(relativeUri);
   }
 
   @override
-  String toString() => _file.toString();
+  String toString() => file.toString();
 }
 
 /**
  * An in-memory implementation of [Folder].
  */
 class _MemoryFolder extends _MemoryResource implements Folder {
   _MemoryFolder(MemoryResourceProvider provider, String path)
       : super(provider, path);
 
   @override
@@ skipping 97 matching lines @@
   bool operator ==(other) {
     if (runtimeType != other.runtimeType) {
       return false;
     }
     return path == other.path;
   }
 
   @override
   String toString() => path;
 }