Clean up activity manager process state tests.

There are now constants for process states, so if/when their
strings change in the future it won't be horrible.  Also removed
the need to pass in a timeout everywhere.

And fixed the new heavy weight tests to be less flaky around when
a window gets focus (though there is also some platform work that
is happening in parallel to further improve this, and ideas needed
to actually completely fix it).

Test: this one
Change-Id: If2136d39561374e04d3f3ce940c09d9382904f57
9 files changed