Fix up all the easy virtual ... SK_OVERRIDE cases.

gm/mixedxfermodes.cpp

Index: gm/mixedxfermodes.cpp
diff --git a/gm/mixedxfermodes.cpp b/gm/mixedxfermodes.cpp
index 3e5ee7d1d3943b5dab2d57dfcbfd843d9dcdfd87..331d1ec0bdc72bfd6a4efa4b4b5dea6b0e8b1d9f 100644
--- a/gm/mixedxfermodes.cpp
+++ b/gm/mixedxfermodes.cpp
@@ -31,11 +31,11 @@ protected:
         kNumShapeTypes
     };
 
-    virtual SkString onShortName() SK_OVERRIDE {
+    SkString onShortName() SK_OVERRIDE {
         return SkString("mixed_xfermodes");
     }
 
-    virtual SkISize onISize() SK_OVERRIDE {
+    SkISize onISize() SK_OVERRIDE {
         return SkISize::Make(790, 640);
     }
 
@@ -87,7 +87,7 @@ protected:
         }
     }
 
-    virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {
+    void onDraw(SkCanvas* canvas) SK_OVERRIDE {
         if (NULL == fBG.get()) {
             static uint32_t kCheckerPixelData[] = { 0xFFFFFFFF,
                                                     0xFFCCCCCC,