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

site/user/sample/hello.md

 Creating a Skia "Hello World!"
 ==============================
 
 This tutorial will guide you through the steps to create a Hello World Desktop
 application in Skia.
 
 Who this tutorial is for:
 -------------------------
 
 This will be useful to you if you want to create a window that can receive
@@ skipping 54 matching lines @@
         HelloTutorial(SkExampleWindow* window)
             : SkExample(window)
         {
             fName = "Tutorial";  // This is how Skia will find your example.
 
             fWindow->setupBackend(SkExampleWindow::kGPU_DeviceType);
            // Another option is the CPU backend:  fWindow->setupBackend(kRaster_DeviceType);
         }
 
     protected:
-        virtual void draw(SkCanvas* canvas) SK_OVERRIDE {
+        void draw(SkCanvas* canvas) SK_OVERRIDE {
             // Clear background
             canvas->drawColor(SK_ColorWHITE);
 
             SkPaint paint;
             // Draw a message with a nice black paint.
             paint.setFlags(SkPaint::kAntiAlias_Flag);
             paint.setColor(SK_ColorBLACK);
             paint.setTextSize(SkIntToScalar(20));
 
             static const char message[] = "Hello World!";
@@ skipping 28 matching lines @@
   * Repeat Step 2 to update our gyp targets and build our example.
   * Run the SkiaExamples, specifying the name of our new example: `$> out/Release/SkiaExamples --match Tutorial`
 
 Step 5: How to iterate through multiple examples
 ------------------------------------------------
 
 If you did not specify an example with the --match flag, or if your match
 string matches more than one example, you can use the *n* key to iterate
 through all of the examples registered.