Magnifier gpu path fix

The y axis was inverted for the offset, which should have been computed on the other side of the magnifying rectangle.

BUG=
R=bsalomon@google.com, senorblanco@google.com, senorblanco@chromium.org

Author: sugoi@chromium.org

Review URL: https://codereview.chromium.org/28273005

git-svn-id: http://skia.googlecode.com/svn/trunk/src@11883 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed