Add a new activity attribute, resumeWhilePausing, that allows an
activity specifying it to immediately start running without waiting
for the previous activity to pause. The recents activity is updated
to use this.
The implementation of this is ultimately fairly simple -- if we are
in the path of resuming such an activity, and find that we first need
to pause the existing activity, then within the activity manager we
do the regular pause flow but act like it has immediately finished
pausing right then so that we can immediately go on to the resume.
To make this clean, we tell the activity when asking it to pause that
it should not come back and tell us it is done, because we aren't in
any way waiting for it.
One potentially important change I needed to make here is the pause
callback no longer provides the saved persistent state, because we
now can't count on that callback happening. I don't think there was
really any utility in this anyway -- all modern apps will have their
save state flow happen as part of stopping, not pausing, so we'll
only capture that saved state when the stop is reported back anyway.
And since we do send the saved state back when stopping, it would
always blow away whatever we had gotten at the pause.
Finally, update the documentation for AppTask.startActivity(), and
fix the implementation handling that to be cleaner -- we need to
deal with inTask first before getting in to "oh noes add NEW_TASK
if this isn't coming from a calling activity" flow.
Change-Id: Ia1da0fac90d7bdbaafdda2e34850d795ce17a39f
a4e102ee58