DevTools: disable highlight in inspected page while recording is in progress

... so that we minimize noise in the recording, as highlight causes compositing.

BUG=317357
R=vsevik@chromium.org

Review URL: https://codereview.chromium.org/68133003

git-svn-id: svn://svn.chromium.org/blink/trunk@161730 bbb929c8-8fbe-4397-9dbb-9b2b20218538