Add missing flattenable registrations and CreateProc() functions;
fixes gm --serialize xfermode test case.



git-svn-id: http://skia.googlecode.com/svn/trunk@1199 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/effects/SkPixelXorXfermode.cpp b/src/effects/SkPixelXorXfermode.cpp
index 0fb0494..f4a74ee 100644
--- a/src/effects/SkPixelXorXfermode.cpp
+++ b/src/effects/SkPixelXorXfermode.cpp
@@ -43,3 +43,6 @@
     return SkNEW_ARGS(SkPixelXorXfermode, (rb));
 }
 
+static SkFlattenable::Registrar
+    gSkPixelXorXfermodeReg("SkPixelXorXfermode",
+                           SkPixelXorXfermode::CreateProc);