Add FileSystemWatcher class to dart:io.

runtime/bin/file_patch.dart

Index: runtime/bin/file_patch.dart
diff --git a/runtime/bin/file_patch.dart b/runtime/bin/file_patch.dart
index c9e4fccb01e9df906a65981a24a627cb2d68cdd8..11fd9fccccd380b55ec5dd29b3158c05dc6200a1 100644
--- a/runtime/bin/file_patch.dart
+++ b/runtime/bin/file_patch.dart
@@ -42,6 +42,17 @@ patch class _RandomAccessFile {
   /* patch */ static _flush(int id) native "File_Flush";
 }
 
+patch class FileSystemWatcher {
+  int _initWatcher() native "FileSystemWatcher_Init";
+  void _stopWatcher(int id) native "FileSystemWatcher_Stop";
+  int _getSocketId(int id, int pathId) native "FileSystemWatcher_GetSocketId";
+  int _addPath(int id, String path, int events, bool recursive)
+      native "FileSystemWatcher_AddPath";
+  void _removePath(int id, int pathId) native "FileSystemWatcher_RemovePath";
+  List _readNextEvent(int id, int pathId)
+      native "FileSystemWatcher_ReadNextEvent";
+}
+
 Uint8List _makeUint8ListView(Uint8List source, int offsetInBytes, int length) {
   return new Uint8List.view(source.buffer, offsetInBytes, length);
 }