remove unneeded SK_SUPPORT_LEGACY_PROCXFERMODE

BUG=skia:
R=fmalita@google.com, fmalita@chromium.org

Author: reed@google.com

Review URL: https://codereview.chromium.org/267573003

git-svn-id: http://skia.googlecode.com/svn/trunk@14489 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed