Standardize usage of virtual/override/final in cc/

cc/resources/picture_pile.h

 // Copyright 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.
 
 #ifndef CC_RESOURCES_PICTURE_PILE_H_
 #define CC_RESOURCES_PICTURE_PILE_H_
 
 #include "cc/resources/picture_pile_base.h"
 #include "ui/gfx/rect.h"
 
@@ skipping 36 matching lines @@
   bool is_suitable_for_gpu_rasterization() const {
     return is_suitable_for_gpu_rasterization_;
   }
   void SetUnsuitableForGpuRasterizationForTesting() {
     is_suitable_for_gpu_rasterization_ = false;
   }
 
   void SetPixelRecordDistanceForTesting(int d) { pixel_record_distance_ = d; }
 
  protected:
-  virtual ~PicturePile();
+  ~PicturePile() override;
 
  private:
   friend class PicturePileImpl;
 
   void DetermineIfSolidColor();
 
   bool is_suitable_for_gpu_rasterization_;
   int pixel_record_distance_;
 
   DISALLOW_COPY_AND_ASSIGN(PicturePile);
 };
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_PICTURE_PILE_H_