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

net/base/file_path_watcher_callback.cc

+// 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.
+
+#include "net/base/file_path_watcher_callback.h"
+
+#include "base/callback.h"
+#include "base/files/file_path_watcher.h"
+#include "base/logging.h"
+
+namespace net {
+
+// A FilePathWatcher::Delegate that forwards calls to FilePathWatcherCallback.
+class FilePathWatcherCallback::WatcherDelegate
+    : public base::files::FilePathWatcher::Delegate {
+ public:
+  explicit WatcherDelegate(FilePathWatcherCallback* watcher)
+      : watcher_(watcher) {}
+
+  void Cancel() {
+    watcher_ = NULL;
+  }
+
+  void OnFilePathChanged(const FilePath& path) OVERRIDE {
+    if (watcher_)
+      watcher_->OnFilePathChanged();
+  }
+
+  void OnFilePathError(const FilePath& path) OVERRIDE {
+    if (watcher_)
+      watcher_->OnFilePathError();
+  }
+
+ private:
+  virtual ~WatcherDelegate() {}
+  FilePathWatcherCallback* watcher_;
+};
+
+FilePathWatcherCallback::FilePathWatcherCallback() {
+  // No need to restrict the thread until the state is created in Watch.
+  DetachFromThread();
+}
+
+FilePathWatcherCallback::~FilePathWatcherCallback() {
+  Cancel();
+}
+
+void FilePathWatcherCallback::Cancel() {
+  DCHECK(CalledOnValidThread());
+  if (delegate_) {
+    delegate_->Cancel();
+    delegate_.release();
+  }
+  watcher_.reset(NULL);
+  // All state is gone so it's okay to detach from thread.
+  DetachFromThread();
+}
+
+bool FilePathWatcherCallback::Watch(
+    const FilePath& path,
+    const base::Callback<void(bool succeeded)>& callback) {
+  DCHECK(CalledOnValidThread());
+  if (delegate_)
+    delegate_->Cancel();
+  watcher_.reset(new base::files::FilePathWatcher());
+  delegate_ = new WatcherDelegate(this);
+  if (watcher_->Watch(path, delegate_.get()))
+    return true;
+
+  Cancel();
+  return false;
+}
+
+void FilePathWatcherCallback::OnFilePathChanged() {
+  DCHECK(CalledOnValidThread());
+  callback_.Run(true);
+}
+
+void FilePathWatcherCallback::OnFilePathError() {
+  DCHECK(CalledOnValidThread());
+  base::Callback<void(bool succeeded)> callback = callback_;
+  Cancel();
+  callback.Run(false);
+}
+
+}  // namespace net
+