DevTools: Counter values update should not cause whole page relayout

+ made counter colors more bright to align with the rest of timeline palette.

R=caseq@chromium.org

Review URL: https://codereview.chromium.org/104593013

git-svn-id: svn://svn.chromium.org/blink/trunk@163867 bbb929c8-8fbe-4397-9dbb-9b2b20218538