Events for window's content change should be dispatched only for the active window.

1. Accessibility events for changes in the content of a given window, such as
   click, focus, etc. are dispatched to clients only if they come from the
   active window.

   Events for changes in the state of a window, such as window got input focus
   or a notification appeared, are always dispatched. The notification events
   do not contain source, so a client cannot introspect the notification area
   (unless the user explicitly touches it which generates hove events). The
   events for a window getting input focus change the active window so they
   have to be dispatched.

   Events that are a result of the user touching the screen, such as hover
   enter, first tocuh, etc. should always be dispatched.

bug:7282006

Change-Id: I96b79189f8571285175d9660a22394cc84f39559