Remove deadcode for sRGB image shading.

Change-Id: I9d98da67d97b64ab55cf44b9ae447882dccda1ca
Reviewed-on: https://skia-review.googlesource.com/20695
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Herb Derby <herb@google.com>
42 files changed