Implement Sk2f::Store2

Bug: skia:
Change-Id: Ieedd05ced376a7604936e9d2729fc20a8669496e
Reviewed-on: https://skia-review.googlesource.com/115531
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
3 files changed