Remove ref-counting from FilePathWatcher.

base/files/file_path_watcher_win.cc

Index: base/files/file_path_watcher_win.cc
diff --git a/base/files/file_path_watcher_win.cc b/base/files/file_path_watcher_win.cc
index 65c13dae74abf1194da34ca80d7278d235e60339..3557514f66e03ed951ed9f999583ca6ec9eb0d9c 100644
--- a/base/files/file_path_watcher_win.cc
+++ b/base/files/file_path_watcher_win.cc
@@ -10,6 +10,7 @@
 #include "base/files/file_util.h"
 #include "base/logging.h"
 #include "base/macros.h"
+#include "base/memory/ptr_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/threading/sequenced_task_runner_handle.h"
 #include "base/time/time.h"
@@ -25,6 +26,7 @@ class FilePathWatcherImpl : public FilePathWatcher::PlatformDelegate,
   FilePathWatcherImpl()
       : handle_(INVALID_HANDLE_VALUE),
         recursive_watch_(false) {}
+  ~FilePathWatcherImpl() override;
 
   // FilePathWatcher::PlatformDelegate:
   bool Watch(const FilePath& path,
@@ -36,8 +38,6 @@ class FilePathWatcherImpl : public FilePathWatcher::PlatformDelegate,
   void OnObjectSignaled(HANDLE object) override;
 
  private:
-  ~FilePathWatcherImpl() override {}
-
   // Setup a watch handle for directory |dir|. Set |recursive| to true to watch
   // the directory sub trees. Returns true if no fatal error occurs. |handle|
   // will receive the handle value if |dir| is watchable, otherwise
@@ -78,6 +78,10 @@ class FilePathWatcherImpl : public FilePathWatcher::PlatformDelegate,
   DISALLOW_COPY_AND_ASSIGN(FilePathWatcherImpl);
 };
 
+FilePathWatcherImpl::~FilePathWatcherImpl() {
+  DCHECK(!task_runner() || task_runner()->RunsTasksOnCurrentThread());
+}
+
 bool FilePathWatcherImpl::Watch(const FilePath& path,
                                 bool recursive,
                                 const FilePathWatcher::Callback& callback) {
@@ -269,7 +273,7 @@ void FilePathWatcherImpl::DestroyWatch() {
 
 FilePathWatcher::FilePathWatcher() {
   sequence_checker_.DetachFromSequence();
-  impl_ = new FilePathWatcherImpl();
+  impl_ = MakeUnique<FilePathWatcherImpl>();
 }
 
 }  // namespace base