Revert "remove linear sRGB singleton"

This reverts commit b03b80066bf9de4775fd8e58dc132c2ddf9c81ec.

Reason for revert:  !@#$%^&*

Original change's description:
> remove linear sRGB singleton
> 
> Cq-Include-Trybots: luci.chromium.try:linux-blink-rel
> Change-Id: I01e2515cfa8e5356ee862ea7184bb7ceb4c9176f
> Reviewed-on: https://skia-review.googlesource.com/c/192038
> Commit-Queue: Mike Klein <mtklein@google.com>
> Reviewed-by: Brian Osman <brianosman@google.com>

TBR=mtklein@google.com,brianosman@google.com

Change-Id: Ic88368e193aaa48b9aa6d3a6c145377681b2a5db
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Cq-Include-Trybots: luci.chromium.try:linux-blink-rel
Reviewed-on: https://skia-review.googlesource.com/c/194005
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
4 files changed