WebGL local html file loading fails

[Daylight]

I am trying to use WebGL with the fancy-browser (webenginewidgets) example. When I open an html file with embedded webgl content from the web - it works, but when I open exactly the same html from local filesystem - the behaviour is unpredictable: sometimes it loads, sometimes - not, after refresh it usualy fails...
http://daylight.ho.ua/ngl.htm - works in fancybrowser example
file:///tmp/ngl.htm - fails
In chromium/firefox both work perfectly
Qt 5.5, ubuntu 14.04 x64
Any suggestions, why this could happen would be appreciated.

[Daylight]

Here are the screenshots depicting the problem: