make WidgetView observer private

PS2:  remove all views when creating the popup pager to keep the dingleberries away
PS3:  add onDetached from window for when BaseStatusBar is killed toggling pie halo appbar etc
PS4:  cleanup

Change-Id: I778dca10ee0cf56c5ba62f76ec75e45d3dc4995b
Merge "make WidgetView observer private" into jb43