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diff --git a/chrome/browser/file_watcher.h b/chrome/browser/file_watcher.h
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+// Copyright (c) 2010 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.
+
+// This module provides a way to monitor a file for changes.
+
+#ifndef CHROME_BROWSER_FILE_WATCHER_H_
+#define CHROME_BROWSER_FILE_WATCHER_H_
+#pragma once
+
+#include "base/basictypes.h"
+#include "base/ref_counted.h"
+#include "chrome/browser/chrome_thread.h"
+
+class FilePath;
+
+// This class lets you register interest in changes on a file. The delegate
+// will get called whenever the file is changed, including created or deleted.
+// WARNING: To be able to get create/delete notifications and to work cross
+// platform, we actually listen for changes to the directory containing
+// the file.
+// WARNING: On OSX and Windows, the OS API doesn't tell us which file in the
+// directory changed.  We work around this by watching the file time, but this
+// can result in some extra notifications if we get other notifications within
+// 2s of the file having changed.
+class FileWatcher {
+ public:
+  // Declares the callback client code implements to receive notifications. Note
+  // that implementations of this interface should not keep a reference to the
+  // corresponding FileWatcher object to prevent a reference cycle.
+  class Delegate : public base::RefCountedThreadSafe<Delegate> {
+   public:
+    virtual ~Delegate() {}
+    virtual void OnFileChanged(const FilePath& path) = 0;
+  };
+
+  FileWatcher();
+  ~FileWatcher() {}
+
+  // Register interest in any changes on the file |path|.
+  // OnFileChanged will be called back for each change to the file.  Any
+  // background operations will be ran on |backend_thread_id|.  Note: The
+  // directory containing |path| must exist before you try to watch the file.
+  // Returns false if the watch can't be added.
+  bool Watch(const FilePath& path, Delegate* delegate) {
+    DCHECK(ChromeThread::CurrentlyOn(ChromeThread::FILE));
+    return impl_->Watch(path, delegate);
+  }
+
+  // Used internally to encapsulate different members on different platforms.
+  class PlatformDelegate
+      : public base::RefCountedThreadSafe<PlatformDelegate,
+                                          ChromeThread::DeleteOnFileThread> {
+   public:
+    virtual ~PlatformDelegate() {}
+
+    virtual bool Watch(const FilePath& path, Delegate* delegate) = 0;
+  };
+
+ private:
+  scoped_refptr<PlatformDelegate> impl_;
+
+  DISALLOW_COPY_AND_ASSIGN(FileWatcher);
+};
+
+#endif  // CHROME_BROWSER_FILE_WATCHER_H_