[net] Add DNS-related signals and NetLog to NetworkChangeNotifier.

net/base/file_path_watcher_callback.h

Index: net/base/file_path_watcher_callback.h
diff --git a/net/base/file_path_watcher_callback.h b/net/base/file_path_watcher_callback.h
new file mode 100644
index 0000000000000000000000000000000000000000..1f3bb94009553597f6fddb8728f09667d406a91f
--- /dev/null
+++ b/net/base/file_path_watcher_callback.h
@@ -0,0 +1,60 @@
+// Copyright (c) 2012 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.
+
+#ifndef NET_FILE_PATH_WATCHER_CALLBACK_H_
+#define NET_FILE_PATH_WATCHER_CALLBACK_H_
+#pragma once
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/callback.h"
+#include "base/file_path.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/threading/non_thread_safe.h"
+
+namespace base {
+namespace files {
+class FilePathWatcher;
+}
+}
+
+namespace net {
+
+// Convenience wrapper which holds a FilePathWatcher and a
+// FilePathWatcher::Delegate which forwards its calls to a Callback.
+class FilePathWatcherCallback : public base::NonThreadSafe {
+ public:
+  FilePathWatcherCallback();
+  // When deleted, automatically cancels the FilePathWatcher.
+  virtual ~FilePathWatcherCallback();
+
+  // Starts watching the file at |path|. Returns true if Watch succeeds.
+  // If so, the delegate will call callback.Run(true) from OnFilePathChanged and
+  // callback.Run(false) from OnFilePathError. After failure the watch is
+  // cancelled and will have to be restarted. If called again, the previous
+  // watch is cancelled.
+  bool Watch(const FilePath& path,
+             const base::Callback<void(bool succeeded)>& callback);
+
+  // Cancels the current watch.
+  void Cancel();
+
+ private:
+  class WatcherDelegate;
+
+  void OnFilePathChanged();
+  void OnFilePathError();
+
+  base::Callback<void(bool succeeded)> callback_;
+  scoped_ptr<base::files::FilePathWatcher> watcher_;
+  scoped_refptr<WatcherDelegate> delegate_;
+  DISALLOW_COPY_AND_ASSIGN(FilePathWatcherCallback);
+};
+
+}  // namespace net
+
+#endif  // NET_FILE_PATH_WATCHER_CALLBACK_H_
+