The dashboard automatically marks 'frames' as 'lower is better', while
'score' is automatically marked as 'higher is better'. Hence, use
score instead of frames.

BUG=468852

Change-Id: I02b3a9e4b74989793d4bfbf21a94e43670b3e028
Reviewed-on: https://chromium-review.googlesource.com/266522Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>