Fix calibration in chrome 43+
Fix calibration in chrome 43+

Chrome 43 changed rendering method and due to antialising calibration
script no longer produces expected result. Fixed by using PNG image
instead of creating expected pattern with DOM elements.

racing-post/gemini,gemini-testing/gemini,HDevel/gemini,varya/gemini,pazone/gemini,pazone/gemini,vladislav-sevostyanov/gemini,varya/gemini,racing-post/gemini,HDevel/gemini,sergesemashko/gemini