update image doc and minor bookmaker fixes

image doc is still a work in progress.
Update online version to latest; updating
include header is still a ways off.

Remove SkPaint::flatten() example since
parameter is not publicly accessible.

Minor changes to fix typedef and std::function
references.

TBR=rmistry@google.com
Docs-Preview: https://skia.org/?cl=87120
Bug: skia:6898
Change-Id: I3553bc5fca97c5997aa61ea034b5ca10cb10df75
Reviewed-on: https://skia-review.googlesource.com/87120
Reviewed-by: Cary Clark <caryclark@skia.org>
Commit-Queue: Cary Clark <caryclark@skia.org>
11 files changed