Update ui::PointerEvent to support mouse wheel and capture change events.

ui/views/pointer_watcher.h

Index: ui/views/pointer_watcher.h
diff --git a/ui/views/pointer_watcher.h b/ui/views/pointer_watcher.h
index 8270683214e99f946e0629d433a31662fb71d3a0..008187180346388f91725772325b51b4bb3c41fc 100644
--- a/ui/views/pointer_watcher.h
+++ b/ui/views/pointer_watcher.h
@@ -35,10 +35,6 @@ class VIEWS_EXPORT PointerWatcher {
                                       const gfx::Point& location_in_screen,
                                       Widget* target) = 0;
 
-  // PointerWatcher is informed of capture changes as it's common to create a

[sky, 2016/08/22 20:51:45]

Please update the description to indicate capture is sent through
OnPointerEventObserved, and that for capture the target is always null.

[riajiang, 2016/08/22 22:00:19]

Done.

-  // MouseEvent of type ui::ET_MOUSE_CAPTURE_CHANGED on capture change.
-  virtual void OnMouseCaptureChanged() {}
-
  protected:
   virtual ~PointerWatcher() {}