FLUID-4956: Browser hack to fix panel scrolling

The panels in the fat panel had two scrollable areas in webkit browsers, which caused them to look clipped. I have made  a simple browser detection hack in the fat panel's iframe to set the width to 225em when in safari or chrome.
Merge remote-tracking branch 'jobara/FLUID-4956' into demo

* jobara/FLUID-4956:
  FLUID-4956: Browser hack to fix panel scrolling