Remove stale gradient color space assert

SkGradientShaderBase asserts gammaIsLinear() -- but we don't enforce
this in factories.

Based on comments, this may be a stale restriction.  Can we drop it?

Bug: chromium:798208
Change-Id: Id9639cb2bb87f112b26c05372f2a3181c139e5ec
Reviewed-on: https://skia-review.googlesource.com/123860
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
1 file changed