Use FSEvents for recursive file watch on Mac

base/files/file_path_watcher.cc

Index: base/files/file_path_watcher.cc
diff --git a/base/files/file_path_watcher.cc b/base/files/file_path_watcher.cc
index 49e0a237f69a71680e8611b97bdd34f379874ef0..b17354197d4fda6239a178c97f64b2dcf221ab62 100644
--- a/base/files/file_path_watcher.cc
+++ b/base/files/file_path_watcher.cc
@@ -10,6 +10,10 @@
 #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() {
@@ -22,6 +26,19 @@ void FilePathWatcher::CancelWatch(
   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) {
 }