Revert 52613 - Revert 52608 - Add and alternative GetAppOutput() to process_u...

Revert 52613 - Revert 52608 - Add and alternative GetAppOutput() to process_util that takes a timeout.

[Undoing the revert to see if the failure wasn't a flake.... Revert if the
original failure, below, occurs again.]

["base_unittests" didn't exit cleanly on "Chromium Linux x64" but was killed due
to timeout.]

Contributed by tessamac@chromium.org

TEST=none
BUG=47356
Review URL: http://codereview.chromium.org/2810014
Patch from Tessa MacDuff <tessamac@chromium.org>;.

TBR=viettrungluu@chromium.org, tessamac@chromium.org
Review URL: http://codereview.chromium.org/3012004

TBR=viettrungluu@chromium.org, tessamac@chromium.org

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=53903