Update iOS FileSystemWatcher::WatchPath signature

runtime/bin/file_system_watcher_macos.cc

 // Copyright (c) 2013, 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.
 
 #include "platform/globals.h"
 #if defined(HOST_OS_MACOS)
 
 #include "bin/file_system_watcher.h"
 
 #if !HOST_OS_IOS
@@ skipping 398 matching lines @@
 
 void FileSystemWatcher::UnwatchPath(intptr_t id, intptr_t path_id) {}
 
 intptr_t FileSystemWatcher::Init() {
   return -1;
 }
 
 void FileSystemWatcher::Close(intptr_t id) {}
 
 intptr_t FileSystemWatcher::WatchPath(intptr_t id,
+                                      Namespace* namespc,
                                       const char* path,
                                       int events,
                                       bool recursive) {
   return -1;
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // !HOST_OS_IOS
 #endif  // defined(HOST_OS_MACOS)