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

ui/gfx/color_analysis_unittest.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/color_analysis.h"
 
 #include <vector>
 
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/skia/include/core/SkColor.h"
@@ skipping 90 matching lines @@
 
   void Reset() {
     prebaked_sample_results_.clear();
     ResetCounter();
   }
 
   void ResetCounter() {
     current_result_index_ = 0;
   }
 
-  virtual int GetSample(int width, int height) {
+  virtual int GetSample(int width, int height) OVERRIDE {
     if (current_result_index_ >= prebaked_sample_results_.size()) {
       current_result_index_ = 0;
     }
 
     if (prebaked_sample_results_.empty()) {
       return 0;
     }
 
     return prebaked_sample_results_[current_result_index_++];
   }
@@ skipping 49 matching lines @@
   scoped_refptr<base::RefCountedBytes> png(
      new base::RefCountedBytes(
          std::vector<unsigned char>(
              k1x3BlueRed,
              k1x3BlueRed + sizeof(k1x3BlueRed) / sizeof(unsigned char))));
 
   SkColor color = CalculateKMeanColorOfPNG(png, 100, 600, test_sampler);
 
   EXPECT_EQ(color, SkColorSetARGB(0xFF, 0xFF, 0x00, 0x00));
 }