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diff --git a/views/mouse_watcher.h b/views/mouse_watcher.h
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+++ b/views/mouse_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.
+
+#ifndef VIEWS_MOUSE_WATCHER_H_
+#define VIEWS_MOUSE_WATCHER_H_
+#pragma once
+
+#include "base/basictypes.h"
+#include "base/scoped_ptr.h"
+#include "gfx/insets.h"
+
+namespace views {
+
+class View;
+
+// MouseWatcherListener is notified when the mouse moves outside the view.
+class MouseWatcherListener {
+ public:
+  virtual void MouseMovedOutOfView() = 0;
+
+ protected:
+  virtual ~MouseWatcherListener();
+};
+
+// MouseWatcher is used to watch mouse movement and notify its listener when the
+// mouse moves outside the bounds of a view.
+class MouseWatcher {
+ public:
+  // Creates a new MouseWatcher. |hot_zone_insets| is added to the bounds of
+  // the view to determine the active zone. For example, if
+  // |hot_zone_insets.bottom()| is 10, then the listener is not notified if
+  // the y coordinate is between the origin of the view and height of the view
+  // plus 10.
+  MouseWatcher(views::View* host,
+               MouseWatcherListener* listener,
+               const gfx::Insets& hot_zone_insets);
+  ~MouseWatcher();
+
+  // Starts watching mouse movements. When the mouse moves outside the bounds of
+  // the view the listener is notified. |Start| may be invoked any number of
+  // times. If the mouse moves outside the bounds of the view the listener is
+  // notified and watcher stops watching events.
+  void Start();
+
+  // Stops watching mouse events.
+  void Stop();
+
+ private:
+  class Observer;
+
+  // Are we currently observing events?
+  bool is_observing() const { return observer_.get() != NULL; }
+
+  // Notifies the listener and stops watching events.
+  void NotifyListener();
+
+  // View we're listening for events over.
+  views::View* host_;
+
+  // Our listener.
+  MouseWatcherListener* listener_;
+
+  // Insets added to the bounds of the view.
+  const gfx::Insets hot_zone_insets_;
+
+  // Does the actual work of listening for mouse events.
+  scoped_ptr<Observer> observer_;
+
+  DISALLOW_COPY_AND_ASSIGN(MouseWatcher);
+};
+
+}  // namespace views
+
+#endif  // VIEWS_MOUSE_WATCHER_H_