ui: Fix clang warnings about missing virtual and OVERRIDE annotations.

ui/gfx/image/image_skia_operations.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/gfx/image/image_skia_operations.h"
 
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "skia/ext/image_operations.h"
 #include "skia/ext/platform_canvas.h"
@@ skipping 263 matching lines @@
 // ImageSkiaSource which uses SkBitmap::extractSubset to generate image reps
 // for the target image.
 class ExtractSubsetImageSource: public gfx::ImageSkiaSource {
  public:
   ExtractSubsetImageSource(const gfx::ImageSkia& image,
                            const gfx::Rect& subset_bounds)
       : image_(image),
         subset_bounds_(subset_bounds) {
   }
 
-  ~ExtractSubsetImageSource() {
+  virtual ~ExtractSubsetImageSource() {
   }
 
   // gfx::ImageSkiaSource overrides:
   virtual ImageSkiaRep GetImageForScale(ui::ScaleFactor scale_factor) OVERRIDE {
     ImageSkiaRep image_rep = image_.GetRepresentation(scale_factor);
     SkIRect subset_bounds_in_pixel = RectToSkIRect(subset_bounds_.Scale(
         ui::GetScaleFactorScale(image_rep.scale_factor())));
     SkBitmap dst;
     bool success = image_rep.sk_bitmap().extractSubset(&dst,
                                                        subset_bounds_in_pixel);
@@ skipping 155 matching lines @@
     const ImageSkia& source,
     const ShadowValues& shadows) {
   const gfx::Insets shadow_padding = -gfx::ShadowValue::GetMargin(shadows);
   gfx::Size shadow_image_size = source.size();
   shadow_image_size.Enlarge(shadow_padding.width(),
                             shadow_padding.height());
   return ImageSkia(new DropShadowSource(source, shadows), shadow_image_size);
 }
 
 }  // namespace gfx