Do proper NEON checking for SkBoxBlur procs.

TBR=mtklein
BUG=

Review URL: https://codereview.chromium.org/98373003

git-svn-id: http://skia.googlecode.com/svn/trunk@12490 2bbb7eff-a529-9590-31e7-b0007b416f81
3 files changed