Merge changes If31a0d78,I3e327a83,I41e1854e into sc-v2-dev

* changes:
  [Status Bar Refactor] Remove some indirection about minFraction between NotificationPanelViewController and PanelBar.
  [Status Bar Refactor] Remove PanelBar#onPanelFullyOpened and instead handle that logic in the listener callback.
  [Status Bar Refactor] Add a PanelStateChangeListener interface and use it in PanelBar#go.