Layout mangled on HiDPI display

[GoogleCodeExporter]

Reproduction steps
1. Open any page that has JS entries (internal or external doesn't matter, more 
than one really exaggerates the problem)
2. Click the scriptno icon
3. See that the buttons and descriptions are all overlaid on top of each other.

My notebook's display has a resolution of 3280x2160, so I have Chrome running 
at a scaling factor of 1.75 to make things readable. 
"chromium-browser --force-device-scale-factor=1.75" 
When I don't use the scaling factor, everything is ok. When I do, the layout of 
the popup items is overlayed on top of everything. I suspect the root cause is 
layout positioning based on pixels instead of %, em, or something else. This 
makes the product unusable :(

Version: ScriptSafe 1.0.6.18

This is a VERY common occurrence for me, most plugins have the same type of 
problems :)

Original issue reported on code.google.com by Stupidit...@gmail.com on 19 Jun 2015 at 8:33