Add ifdef to avoid "not defined" compiler warnings for VS checks

BUG=skia:2130
R=reed@google.com

Author: hcm@google.com

Review URL: https://codereview.chromium.org/153093004

git-svn-id: http://skia.googlecode.com/svn/trunk@13345 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed