fix off-by-one error in texture coordinate calculations for rrect gpu
blur; output now matches CPU

BUG=
R=bsalomon@google.com

Author: humper@google.com

Review URL: https://codereview.chromium.org/292773003

git-svn-id: http://skia.googlecode.com/svn/trunk@14788 2bbb7eff-a529-9590-31e7-b0007b416f81
2 files changed