base

Fix issue #6404215: New ActionBar auto-hide can conflict with application

The action bar now maintains separate states for the things that can
impact its visibility (calls from the app, action mode, system UI) so
that the changes in these won't incorrectly mix together.

Also added a hack to force the status bar to be shown when showing
the action bar for an action mode, when the UI is in a state where
the action bar would be shown with a gap above where the status bar
is.

Change-Id: Ib0950a7f585c5d2c9e77d11b237ba6e150f15ebd