Make file system watcher compile on Mac OS 106, and add a runtime-call to test if the system suppor…

runtime/bin/file_system_watcher_win.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(TARGET_OS_WINDOWS)
 
 #include "bin/file_system_watcher.h"
 #include "bin/eventhandler.h"
 
 #include <WinIoCtl.h>  // NOLINT
 
 #include "bin/builtin.h"
 #include "bin/log.h"
 #include "bin/utils.h"
 
 
 namespace dart {
 namespace bin {
 
+bool FileSystemWatcher::IsSupported() {
+  return true;
+}
+
+
 intptr_t FileSystemWatcher::WatchPath(const char* path,
                                       int events,
                                       bool recursive) {
   const wchar_t* name = StringUtils::Utf8ToWide(path);
   HANDLE dir = CreateFileW(name,
                            FILE_LIST_DIRECTORY,
                            FILE_SHARE_READ |
                                FILE_SHARE_WRITE |
                                FILE_SHARE_DELETE,
                            NULL,
@@ skipping 61 matching lines @@
     offset += e->NextEntryOffset;
   }
   delete[] buffer;
   return events;
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_WINDOWS)