Use FSEvents for recursive file watch on Mac

base/files/file_path_watcher.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Cross platform methods for FilePathWatcher. See the various platform
 // specific implementation files, too.
 
 #include "base/files/file_path_watcher.h"
 
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
 
+#if defined(OS_MACOSX) && !defined(OS_IOS)
+#include "base/mac/mac_util.h"
+#endif
+
 namespace base {
 
 FilePathWatcher::~FilePathWatcher() {
   impl_->Cancel();
 }
 
 // static
 void FilePathWatcher::CancelWatch(
     const scoped_refptr<PlatformDelegate>& delegate) {
   delegate->CancelOnMessageLoopThread();
 }
 
+// static
+bool FilePathWatcher::RecursiveWatchAvailable() {
+#if defined(OS_MACOSX) && !defined(OS_IOS)
+  // FSEvents isn't available on iOS and is broken on OSX 10.6 and earlier.
+  // See http://crbug.com/54822#c31
+  return mac::IsOSLionOrLater();
+#elif defined(OS_WIN) || defined(OS_LINUX)
+  return true;
+#else
+  return false;
+#endif
+}
+
 FilePathWatcher::PlatformDelegate::PlatformDelegate(): cancelled_(false) {
 }
 
 FilePathWatcher::PlatformDelegate::~PlatformDelegate() {
   DCHECK(is_cancelled());
 }
 
 bool FilePathWatcher::Watch(const FilePath& path,
                             bool recursive,
                             const Callback& callback) {
   DCHECK(path.IsAbsolute());
   return impl_->Watch(path, recursive, callback);
 }
 
 }  // namespace base