commit bb0c067bf37c98cc55b6c79c1174084b1e0c9b0b
author Alex Deymo <deymo@google.com> Wed Mar 09 18:11:12 2016 -0800
committer Alex Deymo <deymo@google.com> Thu Mar 17 14:39:15 2016 -0700
tree e153a13be099ca2df953545a5b91170170bbcdc5
parent c975d7bc6767711c4802e104c4a9d4731910c9be

Implement susped, resume and cancel for the Postinstall action.

This patch sends SIGSTOP/SIGCONT to the running postinstall program to
suspend/resume the child process, and SIGKILL when cancelling it.

Bug: 27272144
TEST=Added unittest to check the signal being sent.

(cherry picked from commit d15c546ed794293d0a63770467a0f3c4c84c6214)

Change-Id: Ie99b406b4d7f73dda4189b7a5a7d627c866055d6