DevTools: fix a few inspector/audits tests

The patch fixes inspector/audits/audits-panel-noimages-functional.html
and inspector/audits/audits-panel-functional.html

BUG=364088, 357079
R=apavlov

Review URL: https://codereview.chromium.org/483683002

git-svn-id: svn://svn.chromium.org/blink/trunk@180448 bbb929c8-8fbe-4397-9dbb-9b2b20218538