remove remaining references to porterduff



git-svn-id: http://skia.googlecode.com/svn/trunk@236 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gm/xfermodes.cpp b/gm/xfermodes.cpp
index 8b0ea65..5a43f4a 100644
--- a/gm/xfermodes.cpp
+++ b/gm/xfermodes.cpp
@@ -63,11 +63,13 @@
     }
     
 protected:
-    SkString onShortName() {
+    virtual SkString onShortName() {
         return SkString("xfermodes");
     }
 
-	SkISize onISize() { return make_isize(790, 480); }
+	virtual SkISize onISize() {
+        return make_isize(790, 480);
+    }
 
     void drawBG(SkCanvas* canvas) {
         canvas->drawColor(SK_ColorWHITE);