Gardening: widen expectations for virtual/gpu/fast/canvas/canvas-overflow-hidden-animation.html

BUG=369615
TBR=ojan

Review URL: https://codereview.chromium.org/275803002

git-svn-id: svn://svn.chromium.org/blink/trunk@173734 bbb929c8-8fbe-4397-9dbb-9b2b20218538