Fix 10.6 build: double -> float.

BUG=skia:
R=robertphillips@google.com, mtklein@google.com, reed@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/209893004

git-svn-id: http://skia.googlecode.com/svn/trunk@13906 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed