Standardize usage of virtual/override/final in cc/

cc/test/pixel_comparator.h

Index: cc/test/pixel_comparator.h
diff --git a/cc/test/pixel_comparator.h b/cc/test/pixel_comparator.h
index 0d418e89d8466d775ba1312e3db91eb5d97164a6..72288583ef2ecee2928f92d81faede8d035114dd 100644
--- a/cc/test/pixel_comparator.h
+++ b/cc/test/pixel_comparator.h
@@ -23,13 +23,13 @@ class PixelComparator {
 class ExactPixelComparator : public PixelComparator {
  public:
   explicit ExactPixelComparator(const bool discard_alpha);
-  virtual ~ExactPixelComparator() {}
+  ~ExactPixelComparator() override {}
 
   // Returns true if the two bitmaps are identical. Otherwise, returns false
   // and report the number of pixels with an error on LOG(ERROR). Differences
   // in the alpha channel are ignored.
-  virtual bool Compare(const SkBitmap& actual_bmp,
-                       const SkBitmap& expected_bmp) const override;
+  bool Compare(const SkBitmap& actual_bmp,
+               const SkBitmap& expected_bmp) const override;
 
  private:
   // Exclude alpha channel from comparison?
@@ -46,13 +46,13 @@ class FuzzyPixelComparator : public PixelComparator {
                        const float avg_abs_error_limit,
                        const int max_abs_error_limit,
                        const int small_error_threshold);
-  virtual ~FuzzyPixelComparator() {}
+  ~FuzzyPixelComparator() override {}
 
   // Computes error metrics and returns true if the errors don't exceed the
   // specified limits. Otherwise, returns false and reports the error metrics on
   // LOG(ERROR). Differences in the alpha channel are ignored.
-  virtual bool Compare(const SkBitmap& actual_bmp,
-                       const SkBitmap& expected_bmp) const override;
+  bool Compare(const SkBitmap& actual_bmp,
+               const SkBitmap& expected_bmp) const override;
 
  private:
   // Exclude alpha channel from comparison?