Always encode images with sRGB encoded pixels

Bug: skia:
Change-Id: Icb25bc21a30e88f21df5b0e267d5a3a05535e44a
Reviewed-on: https://skia-review.googlesource.com/19544
Commit-Queue: Matt Sarett <msarett@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
Reviewed-by: Mike Klein <mtklein@chromium.org>
(cherry picked from commit 1950e0a868774330330555a9a368992218f42240)
Reviewed-on: https://skia-review.googlesource.com/19814
Reviewed-by: Matt Sarett <msarett@google.com>
4 files changed