Maintaining diff for all widget operations instead of just the Views update

When the widget starts lisnening again, it receives all the pending updates
until that point (restricted to the requested widgetIds). When startListening
is called for the first time, the widgetIds is empty and it does not get
any updated. Further calls to startlisting will give the missed updates
for the bound widgets

Bug: 23892701
Change-Id: I3aa06d3e33a0861c19cfd5ced567d5bb3b93d906