Split up SkXfermode::asNewEffectOrCoeff() into asNewEffect(), asCoeff().

R=bsalomon@google.com

Review URL: https://codereview.chromium.org/37593002

git-svn-id: http://skia.googlecode.com/svn/trunk/src@11926 2bbb7eff-a529-9590-31e7-b0007b416f81
3 files changed