base::Bind: Convert FilePathWatcher.

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 7ce64ac49cf1df6eac1bbfdcda45cb71b4e92195..086da1e6968c542f7b5632e47d7727d87beeb060 100644
--- a/base/files/file_path_watcher.cc
+++ b/base/files/file_path_watcher.cc
@@ -17,6 +17,12 @@ FilePathWatcher::~FilePathWatcher() {
   impl_->Cancel();
 }
 
+// static
+void FilePathWatcher::CancelWatch(
+    const scoped_refptr<PlatformDelegate>& delegate) {
+  delegate->CancelOnMessageLoopThread();
+}
+
 bool FilePathWatcher::Watch(const FilePath& path, Delegate* delegate) {
   DCHECK(path.IsAbsolute());
   return impl_->Watch(path, delegate);