Fix error in Palette resize function

This ultimately led to the internal bitmap
used for color extraction being very
very small, which hurt quality. Since we
are now using the correct size, performance
has dropped by roughly 25%.

500 iterations (now vs previously)
Pixel: 3620ms, 2712ms
N5: 14996ms, 12435ms
GN: 31540ms, 24109ms

Test: all pass
BUG: 31392794

Change-Id: I7cc81e9ab2f44895a5ee9f4736d92318f4dfdced
1 file changed