Ok, figured out what caused problems to my BB - but still don't understand why.
So setting LLVM optimization to -O0 done the trick but why does it affect my mobile device only? All desktop browsers are fine with -O3.
Another tiny problem was with webgl shaders, they need a bit more precise control on arithmetic errors.
Summarizing everything, seams Ascii Patrol will have a web port, with requirement for desktop browser to have either canvas 2d or web-gl support while mobile browsers if one lacks of web-gl it may fall into really low frame rates because of unaccelerated 2d canvas.