remove use of xfermode* in procs

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4592

Change-Id: I99f35924ff5325dfac527bb573a86d2d0366e0b3
Reviewed-on: https://skia-review.googlesource.com/4592
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Reed <reed@google.com>
diff --git a/src/effects/SkLayerDrawLooper.cpp b/src/effects/SkLayerDrawLooper.cpp
index 9337198..e72d137 100644
--- a/src/effects/SkLayerDrawLooper.cpp
+++ b/src/effects/SkLayerDrawLooper.cpp
@@ -48,7 +48,7 @@
         default: {
             SkPMColor pmS = SkPreMultiplyColor(src);
             SkPMColor pmD = SkPreMultiplyColor(dst);
-            SkPMColor result = SkXfermode::GetProc((SkXfermode::Mode)mode)(pmS, pmD);
+            SkPMColor result = SkXfermode::GetProc(mode)(pmS, pmD);
             return SkUnPreMultiply::PMColorToColor(result);
         }
     }