Dpr detection when swapping screens

[Miguel A Cardona]

http://codepen.io/anon/pen/MazvMB

When you move from a dpr1 screen to a dpr 2 screen and trigger a new image via resize, you get the correct dpr 2 value being appended. When moving back to a dpr 1 screen from the dpr 2 screen, it remains a dpr2 value. See attached codepen. This relates directly to ticket #4123 in zendesk.