To escape the hell of different pixel densities in mobile phones, I use SVG-files as background images in my css.
Chrome for android seems to render inline-svg
For me, the solution whilst it took a very long to discover was my elements css:
border-radius: 4px;
This fixed my issues, however I have not been able to recreate it over than on the site I have been working on but here is the fiddle that I was trying to recreate the problem on mobile:
http://jsfiddle.net/rc8Hh/31/
Good luck, my advise check if there is a class that might be affecting the drawing of the element.