Add support for almost-recursive watches in Linux DirectoryWatcher

base/directory_watcher_mac.cc

Index: base/directory_watcher_mac.cc
diff --git a/base/directory_watcher_mac.cc b/base/directory_watcher_mac.cc
index d4b3082e994b67bb925d658c0567985573292722..dc3eba61b58bbf508e0ec01f12ac2bc0a3bf83e9 100644
--- a/base/directory_watcher_mac.cc
+++ b/base/directory_watcher_mac.cc
@@ -28,7 +28,7 @@ class DirectoryWatcherImpl : public DirectoryWatcher::PlatformDelegate {
   }
 
   virtual bool Watch(const FilePath& path, DirectoryWatcher::Delegate* delegate,
-                     bool recursive);
+                     MessageLoop* backend_loop, bool recursive);
 
   void OnFSEventsCallback(const FilePath& event_path) {
     DCHECK(!path_.value().empty());
@@ -72,6 +72,7 @@ void FSEventsCallback(ConstFSEventStreamRef stream,
 
 bool DirectoryWatcherImpl::Watch(const FilePath& path,
                                  DirectoryWatcher::Delegate* delegate,
+                                 MessageLoop* backend_loop,
                                  bool recursive) {
   DCHECK(path_.value().empty());  // Can only watch one path.