WebView and Dygraph

[edartuz]

I have a problem with WebView, it can't display charts with Dygraph: 
http://dygraphs.com/gallery/#g/annotations

Lines are not visible: 
http://piccy.info/view3/6591894/dfeafc2dc2af39ed0760afcb9d508546/
The same page loaded in QtWeb browser (also based on Webkit): 
http://piccy.info/view3/6591897/6216c3ba4fd54e3c908ecc0380c323bd/