Touch exploration gesture events change the window id.

1. Touch exploration start and end events are generated
   by the sytstem to provide additional information for
   accessibility services. Since such events do not come
   from any particular window they whould not change the
   id of the window that currently allows exploring its
   content.

2. Touch exploration start and end events were lealing the
   touch explorer class wich is private.

bug:5026258

Change-Id: Icaf3e2bd9566716f2afb876cf8e0d50813b0c76e