I have a project where we are making a patchNine Icon as seen here:
But as you noticed there is small likes between all the patches, this only appears on firefox. I have tried flooring all fractional pixel values to see if that fixed it but it did not.
I tried a number of things on my side with the 9-patch code (trying to offset some positions/width/height by 0.5 and such) but could not come up with a scheme that always worked in Firefox… It really seems to have something with the code that handles scales in Firefox (problems arise when scaling is not an integer value like 2.65 for eg).