Unreviewed gardening. Pixel diffs on scrollbar arrows.

The baselining for this appears to vary by particular windows
platform, so I'm adding "Pass" for now.

TBR=tkent@chromium.org,ojan@chromium.org
BUG=335472

Review URL: https://codereview.chromium.org/149093007

git-svn-id: svn://svn.chromium.org/blink/trunk@166042 bbb929c8-8fbe-4397-9dbb-9b2b20218538