Remove ref-counting from FilePathWatcher.

base/files/file_path_watcher_win.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.
 
 #include "base/files/file_path_watcher.h"
 
 #include "base/bind.h"
 #include "base/files/file.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/logging.h"
 #include "base/macros.h"
-#include "base/memory/ref_counted.h"
+#include "base/memory/ptr_util.h"
 #include "base/threading/sequenced_task_runner_handle.h"
 #include "base/time/time.h"
 #include "base/win/object_watcher.h"
 
 namespace base {
 
 namespace {
 
 class FilePathWatcherImpl : public FilePathWatcher::PlatformDelegate,
                             public base::win::ObjectWatcher::Delegate {
  public:
   FilePathWatcherImpl()
       : handle_(INVALID_HANDLE_VALUE),
         recursive_watch_(false) {}
+  ~FilePathWatcherImpl() override;
 
   // FilePathWatcher::PlatformDelegate:
   bool Watch(const FilePath& path,
              bool recursive,
              const FilePathWatcher::Callback& callback) override;
   void Cancel() override;
 
   // base::win::ObjectWatcher::Delegate:
   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
   // INVALID_HANDLE_VALUE.
   static bool SetupWatchHandle(const FilePath& dir,
                                bool recursive,
                                HANDLE* handle) WARN_UNUSED_RESULT;
 
   // (Re-)Initialize the watch handle.
   bool UpdateWatch() WARN_UNUSED_RESULT;
 
   // Destroy the watch handle.
   void DestroyWatch();
 
   // Callback to notify upon changes.
   FilePathWatcher::Callback callback_;
 
   // Path we're supposed to watch (passed to callback).
   FilePath target_;
 
+  // Set to true in the destructor.
+  bool* was_deleted_ptr_ = nullptr;
+
   // Handle for FindFirstChangeNotification.
   HANDLE handle_;
 
   // ObjectWatcher to watch handle_ for events.
   base::win::ObjectWatcher watcher_;
 
   // Set to true to watch the sub trees of the specified directory file path.
   bool recursive_watch_;
 
   // Keep track of the last modified time of the file.  We use nulltime
   // to represent the file not existing.
   Time last_modified_;
 
   // The time at which we processed the first notification with the
   // |last_modified_| time stamp.
   Time first_notification_;
 
   DISALLOW_COPY_AND_ASSIGN(FilePathWatcherImpl);
 };
 
+FilePathWatcherImpl::~FilePathWatcherImpl() {
+  DCHECK(!task_runner() || task_runner()->RunsTasksOnCurrentThread());
+  if (was_deleted_ptr_)
+    *was_deleted_ptr_ = true;
+}
+
 bool FilePathWatcherImpl::Watch(const FilePath& path,
                                 bool recursive,
                                 const FilePathWatcher::Callback& callback) {
   DCHECK(target_.value().empty());  // Can only watch one path.
 
   set_task_runner(SequencedTaskRunnerHandle::Get());
   callback_ = callback;
   target_ = path;
   recursive_watch_ = recursive;
 
@@ skipping 21 matching lines @@
   DCHECK(task_runner()->RunsTasksOnCurrentThread());
   set_cancelled();
 
   if (handle_ != INVALID_HANDLE_VALUE)
     DestroyWatch();
 
   callback_.Reset();
 }
 
 void FilePathWatcherImpl::OnObjectSignaled(HANDLE object) {
-  DCHECK(object == handle_);
-  // Make sure we stay alive through the body of this function.
-  scoped_refptr<FilePathWatcherImpl> keep_alive(this);
+  DCHECK(task_runner()->RunsTasksOnCurrentThread());
+  DCHECK_EQ(object, handle_);
+  DCHECK(!was_deleted_ptr_);
+
+  bool was_deleted = false;
+  was_deleted_ptr_ = &was_deleted;
 
   if (!UpdateWatch()) {
     callback_.Run(target_, true /* error */);
     return;
   }
 
   // Check whether the event applies to |target_| and notify the callback.
   File::Info file_info;
   bool file_exists = GetFileInfo(target_, &file_info);
   if (recursive_watch_) {
@@ skipping 29 matching lines @@
       // Stop further notifications for this |last_modification_| time stamp.
       first_notification_ = Time();
     }
     callback_.Run(target_, false);
   } else if (!file_exists && !last_modified_.is_null()) {
     last_modified_ = Time();
     callback_.Run(target_, false);
   }
 
   // The watch may have been cancelled by the callback.
-  if (handle_ != INVALID_HANDLE_VALUE)
+  if (!was_deleted) {
     watcher_.StartWatchingOnce(handle_, this);
+    was_deleted_ptr_ = nullptr;
+  }
 }
 
 // static
 bool FilePathWatcherImpl::SetupWatchHandle(const FilePath& dir,
                                            bool recursive,
                                            HANDLE* handle) {
   *handle = FindFirstChangeNotification(
       dir.value().c_str(),
       recursive,
       FILE_NOTIFY_CHANGE_FILE_NAME | FILE_NOTIFY_CHANGE_SIZE |
@@ skipping 76 matching lines @@
 void FilePathWatcherImpl::DestroyWatch() {
   watcher_.StopWatching();
   FindCloseChangeNotification(handle_);
   handle_ = INVALID_HANDLE_VALUE;
 }
 
 }  // namespace
 
 FilePathWatcher::FilePathWatcher() {
   sequence_checker_.DetachFromSequence();
-  impl_ = new FilePathWatcherImpl();
+  impl_ = MakeUnique<FilePathWatcherImpl>();
 }
 
 }  // namespace base