First pass comments to document SkReflected.h

Bug: skia:
Change-Id: I6fe50ef0f783a9093090037c4b22af1400c0136e
Reviewed-on: https://skia-review.googlesource.com/c/193363
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
1 file changed