Added a base::Callback interface to FilePathWatcher.

base/files/file_path_watcher.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.
 
 // Cross platform methods for FilePathWatcher. See the various platform
 // specific implementation files, too.
 
 #include "base/files/file_path_watcher.h"
 
 #include "base/logging.h"
 #include "base/message_loop.h"
 
 namespace base {
 namespace files {
 
+namespace {
+
+// A delegate implementation for the callback interface.
+class FilePathWatcherDelegate : public base::files::FilePathWatcher::Delegate {
+ public:
+  explicit FilePathWatcherDelegate(const FilePathWatcher::Callback& callback)
+      : callback_(callback) {}
+
+  // FilePathWatcher::Delegate implementation.
+  virtual void OnFilePathChanged(const FilePath& path) OVERRIDE {
+    callback_.Run(path, false);
+  }
+
+  virtual void OnFilePathError(const FilePath& path) OVERRIDE {
+    callback_.Run(path, true);
+  }
+
+ private:
+  virtual ~FilePathWatcherDelegate() {}
+
+  FilePathWatcher::Callback callback_;
+
+  DISALLOW_COPY_AND_ASSIGN(FilePathWatcherDelegate);
+};
+
+}  // namespace
+
 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);
 }
 
 FilePathWatcher::PlatformDelegate::PlatformDelegate(): cancelled_(false) {
 }
 
 FilePathWatcher::PlatformDelegate::~PlatformDelegate() {
   DCHECK(is_cancelled());
 }
 
+bool FilePathWatcher::Watch(const FilePath& path, const Callback& callback) {
+  return Watch(path, new FilePathWatcherDelegate(callback));
+}
+
 }  // namespace files
 }  // namespace base