factories should return baseclass, allowing the impl to specialize

include/effects/SkPixelXorXfermode.h

Index: include/effects/SkPixelXorXfermode.h
diff --git a/include/effects/SkPixelXorXfermode.h b/include/effects/SkPixelXorXfermode.h
index 8b7f3388ff705c82364c30b928ecb18f1e9d8b72..f2fe47156cc10d8f91a9b96f511efbfd28633767 100644
--- a/include/effects/SkPixelXorXfermode.h
+++ b/include/effects/SkPixelXorXfermode.h
@@ -17,19 +17,18 @@
 */
 class SK_API SkPixelXorXfermode : public SkXfermode {
 public:
-    static SkPixelXorXfermode* Create(SkColor opColor) { return new SkPixelXorXfermode(opColor); }
+    static SkXfermode* Create(SkColor opColor) { return new SkPixelXorXfermode(opColor); }
 
     SK_TO_STRING_OVERRIDE()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkPixelXorXfermode)
 
 protected:
-    explicit SkPixelXorXfermode(SkColor opColor) : fOpColor(opColor) {}
     void flatten(SkWriteBuffer&) const override;
-
-    // override from SkXfermode
     SkPMColor xferColor(SkPMColor src, SkPMColor dst) const override;
 
 private:
+    explicit SkPixelXorXfermode(SkColor opColor) : fOpColor(opColor) {}
+
     SkColor fOpColor;
 
     typedef SkXfermode INHERITED;