Introduce NON_ZERO_DURATION for animation unit tests
Animations are usually disabled in unit tests for performance. However, to
test the animation system itself some tests request "normal" durations.
Under some conditions (remote desktop, animation disabled for accessibility)
the "normal" duration could still be zero.
This was causing test failures and use-after-frees in ash_unittests on the
drmemory bots and for developers using remote desktop.
Introduce NON_ZERO_DURATION to signal that animation must be enabled and the
duration must be non-zero, but other than that can be as short as possible.
BUG=397478,396969
TEST=ash_unittests on drmemory, Windows and Chrome OS bots
Review URL: https://codereview.chromium.org/
420013002
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@286089 0039d316-1c4b-4281-b951-d872f2087c98