WebKit incorrectly strokes zero-width/height rectangles
I'm not sure why this is incorrect, but the W3C test seems to suggest we're wrong here.
Firefox and Opera both agree with the W3C results on the two sub-tests we fail here.
Same trouble here:
Created attachment 13148 [details]
This should be a simple but worthwhile fix.
Seems low risk and improves correctness. r=me
Landed in r19600.