Fix performance trybots.
Fix performance trybots.

gclient revert can no longer run now that we're using botupdate.
This works around the issue by using git reset --hard.

BUG=401129
NOTRY=True

Review URL: https://codereview.chromium.org/457793003

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@288490 0039d316-1c4b-4281-b951-d872f2087c98

ondra-novak/chromium.src,ondra-novak/chromium.src,littlstar/chromium.src,ondra-novak/chromium.src,ondra-novak/chromium.src,littlstar/chromium.src,littlstar/chromium.src,ondra-novak/chromium.src,ondra-novak/chromium.src,bright-sparks/chromium-spacewalk,littlstar/chromium.src,ondra-novak/chromium.src,ondra-novak/chromium.src,littlstar/chromium.src,bright-sparks/chromium-spacewalk,bright-sparks/chromium-spacewalk,bright-sparks/chromium-spacewalk,littlstar/chromium.src,bright-sparks/chromium-spacewalk,ondra-novak/chromium.src,bright-sparks/chromium-spacewalk,bright-sparks/chromium-spacewalk,littlstar/chromium.src,bright-sparks/chromium-spacewalk,littlstar/chromium.src,bright-sparks/chromium-spacewalk