Revert 162313 "Turn off BitmapImageTest on windows"

ernstm@ said he might fixed the issue, so give it a try.

We still have no idea why XP (DEPS) and XP behaves differently.

> 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

TBR=zmo@chromium.org,ernstm@chromium.org,eseidel@chromium.org

Review URL: https://codereview.chromium.org/81583002

git-svn-id: svn://svn.chromium.org/blink/trunk@162488 bbb929c8-8fbe-4397-9dbb-9b2b20218538