Also use again the taskkill method, recently removed in
https://codereview.chromium.org/1156133006/

BUG=chromium:485932
LOG=n
TBR=jkummerow@chromium.org
NOTREECHECKS=true

Review URL: https://codereview.chromium.org/1177903005

Cr-Commit-Position: refs/heads/master@{#29001}