Remove unpremul/remul from SkArithmeticMode, both raster and GPU, since the SVG spec actually defin…

gm/arithmode.cpp

Index: gm/arithmode.cpp
diff --git a/gm/arithmode.cpp b/gm/arithmode.cpp
index 63be6c387166660f22c03bcc98c3baad3ecac90a..ab509f86f8bad4d7746da952973b1eaeac3de107 100644
--- a/gm/arithmode.cpp
+++ b/gm/arithmode.cpp
@@ -111,7 +111,7 @@ protected:
             SkRect rect = SkRect::MakeXYWH(x, y, SkIntToScalar(WW), SkIntToScalar(HH));
             canvas->saveLayer(&rect, NULL);
             canvas->drawBitmap(dst, x, y, NULL);
-            SkXfermode* xfer = SkArithmeticMode::Create(k[0], k[1], k[2], k[3]);
+            SkXfermode* xfer = SkArithmeticMode::Create(k[0], k[1], k[2], k[3], true);
             SkPaint paint;
             paint.setXfermode(xfer)->unref();
             canvas->drawBitmap(src, x, y, &paint);