Move all SkReadBuffer member initialization to header

Change-Id: I25e4626f55ce42aa505ae1760c3461a77e4a6ac0
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/296042
Commit-Queue: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
Auto-Submit: Brian Osman <brianosman@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
2 files changed