Revert of Delete SkColorSpace::kUnknown_Named, remove fNamed field (patchset #1 id...

Revert of Delete SkColorSpace::kUnknown_Named, remove fNamed field (patchset #1 id:20001 of https://codereview.chromium.org/2302413002/ )

Reason for revert:
This CL introduced two static initializers (gAdobeRGB and gSRGB) which are causing a sizes regression on Chromium builders:

https://build.chromium.org/p/chromium/builders/Linux%20x64/builds/24981

Original issue's description:
> Delete SkColorSpace::kUnknown_Named, remove fNamed field
>
> BUG=skia:
> GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2302413002
>
> Committed: https://skia.googlesource.com/skia/+/54682e856cb66c653bc7e253981a421a2618398e

TBR=reed@google.com,brianosman@google.com,msarett@google.com
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=skia:5724

Review-Url: https://codereview.chromium.org/2306313002