Add missing SK_OVERRIDE

gm/colortypexfermode.cpp

Index: gm/colortypexfermode.cpp
diff --git a/gm/colortypexfermode.cpp b/gm/colortypexfermode.cpp
index 51cb7eb7c30584dd71b64730fed2c9739dd4b086..1b6e2894ae724578fdf65278ceb3110f27afe44e 100644
--- a/gm/colortypexfermode.cpp
+++ b/gm/colortypexfermode.cpp
@@ -54,15 +54,15 @@ public:
     }
 
 protected:
-    virtual SkString onShortName() {
+    virtual SkString onShortName() SK_OVERRIDE {
         return SkString("colortype_xfermodes");
     }
 
-    virtual SkISize onISize() {
+    virtual SkISize onISize() SK_OVERRIDE {
         return SkISize::Make(400, 640);
     }
 
-    virtual void onDraw(SkCanvas* canvas) {
+    virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {
         canvas->translate(SkIntToScalar(10), SkIntToScalar(20));
 
         const struct {