change SkAnnotation to not inherit from SkFlattenable (does not need dynamic factories)

BUG=
R=scroggo@google.com

Review URL: https://codereview.chromium.org/26606004

git-svn-id: http://skia.googlecode.com/svn/trunk/src@11762 2bbb7eff-a529-9590-31e7-b0007b416f81
6 files changed