Merge "Use killProcessGroup when killing app zygote." into rvc-dev am: 0a8ef2b4

    @GuardedBy("mLock")

    private void stopZygoteLocked() {

        if (mZygote != null) {

            // Close the connection and kill the zygote process. This will not cause

            // child processes to be killed by itself.

            mZygote.close();

            Process.killProcess(mZygote.getPid());

            // use killProcessGroup() here, so we kill all untracked children as well.

            Process.killProcessGroup(mZygoteUid, mZygote.getPid());

            mZygote = null;

        }

    }