Turn off BitmapImageTest on windows

BUG=321184
TEST=Webkit XP (DEPS) bots, webkit_unit_tests green
TBR=schenney@chromium.org

Review URL: https://codereview.chromium.org/67963003

git-svn-id: svn://svn.chromium.org/blink/trunk@162313 bbb929c8-8fbe-4397-9dbb-9b2b20218538