Fixes for blurroundrect gm/bench.

Simplify naming/various cases.
Have an atlas of gms, rather than several different images.
In the bench, pull non rendering out of the loop.
Use meaningful enums instead of integers where appropriate.
Add comments.

Addresses comments in https://codereview.chromium.org/52793005/

R=robertphillips@google.com

Review URL: https://codereview.chromium.org/59983004

git-svn-id: http://skia.googlecode.com/svn/trunk@12144 2bbb7eff-a529-9590-31e7-b0007b416f81
2 files changed