gradients does not support spreadMethod
This is easy to see in this test case:
There is no support for this type of thing in CG, so we would have to do our own. This is an extremely
uncommon feature, so this is very low priority.
This is a pretty obscure feature. It would be nice to support this (and we'll likely have to, since the W3C 1.1 test suite covers it), however it's not particularly high priority work.
spreadMethod=pad is supported, but that:
Only CG doesn't support spreadMethods.
I have some WIP code in bug 28152 to synthesize repeating gradients. Reflection would not be hard either.
I don't think I would call it "extremely" uncommon. Hard to implement perhaps, but a useful part of SVG that has been in the spec since the beginning.
FWIW, Firefox seems to handle it OK.