Deflake virtual/implsidepainting/inspector/timeline/timeline-network-resource.html

We should not be checking for order of background records, these may be out of
order WRT main thread.

TBR=loislo

Review URL: https://codereview.chromium.org/151373002

git-svn-id: svn://svn.chromium.org/blink/trunk@166201 bbb929c8-8fbe-4397-9dbb-9b2b20218538