virtual/implsidepainting/inspector/timeline/timeline-frames.html is flaky on all bots.

BUG=407915
TBR=hclam@chromium.org

Review URL: https://codereview.chromium.org/530873005

git-svn-id: svn://svn.chromium.org/blink/trunk@181213 bbb929c8-8fbe-4397-9dbb-9b2b20218538