Fix inverted logic in Chrome PFQ.

Currently the Chrome PFQ actually does the opposite of what we want,
and only exits early when there is a new Chrome. This needs to be
inverted.

Besides this, we also need to skip this logic on builders other than
the Chrome PFQ (e.g. branch builders).

BUG=none
TEST=Trybot run of Chrome PFQ.

Change-Id: I200a2edb0f0a944f4fbadaf1d39a794d3da15a57
Previous-Reviewed-on: https://gerrit.chromium.org/gerrit/46801
(cherry picked from commit c5d07210a84d866a95a1cc404ed6008c1658e91c)
Reviewed-on: https://gerrit.chromium.org/gerrit/49736
Reviewed-by: Ryan Cui <rcui@chromium.org>
Tested-by: David James <davidjames@chromium.org>
1 file changed