remove typedef Info

typedef SkImageInfo Info saves a little typing at the cost of
obfuscating the parameter type. It's only used in a couple of
places so remove it.

The documentation catalog has gotten a bit stale, so update
that as well.

Docs-Preview: https://skia.org/?cl=128400
Bug: skia:6898
Change-Id: I621743a2b2d9a78d5f62742501eebf5f4327efa0
Reviewed-on: https://skia-review.googlesource.com/128400
Commit-Queue: Cary Clark <caryclark@skia.org>
Commit-Queue: Brian Salomon <bsalomon@google.com>
Auto-Submit: Cary Clark <caryclark@skia.org>
Reviewed-by: Brian Salomon <bsalomon@google.com>
5 files changed