minor imageinfo fixes

teeny fixes to SkImageInfo.h to get
ready for documenting it. Selected
SkImageInfo.h as Herb discovered that
global enums (especially forward
declared ones) break bookmaker.

TBR=reed@google.com
Bug: skia:6898
Change-Id: I6ecf4f9dd7022c810f3d7a6cfee10fb07aa49aee
Reviewed-on: https://skia-review.googlesource.com/99342
Reviewed-by: Cary Clark <caryclark@skia.org>
Reviewed-by: Cary Clark <caryclark@google.com>
Commit-Queue: Cary Clark <caryclark@skia.org>
1 file changed