Enable strict-virtual-specifiers for iOS builds.

ui/gfx/image/image_ios_unittest.mm

 // Copyright (c) 2014 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.
 
 #import <QuartzCore/QuartzCore.h>
 #import <UIKit/UIKit.h>
 
 #include "base/logging.h"
 #include "base/mac/scoped_cftyperef.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ skipping 28 matching lines @@
       CGBitmapContextCreateImage(context));
   return [UIImage imageWithCGImage:cg_image
                              scale:scale
                        orientation:UIImageOrientationUp];
 }
 
 
 class ImageIOSTest : public testing::Test {
  public:
   ImageIOSTest() {}
-  virtual ~ImageIOSTest() {}
+  ~ImageIOSTest() override {}
 
-  virtual void SetUp() override {
+  void SetUp() override {
     original_scale_factors_ = gfx::ImageSkia::GetSupportedScales();
   }
 
-  virtual void TearDown() override {
+  void TearDown() override {
     gfx::ImageSkia::SetSupportedScales(original_scale_factors_);
   }
 
  private:
   // Used to save and restore the scale factors in effect before this test.
   std::vector<float> original_scale_factors_;
 
   DISALLOW_COPY_AND_ASSIGN(ImageIOSTest);
 };
 
@@ skipping 34 matching lines @@
       EXPECT_EQ(kWidth, imageskia->width());
       EXPECT_EQ(kHeight, imageskia->height());
 
       // TODO(rohitrao): Convert from ImageSkia back to UIImage.  This should
       // scale the image based on the current set of supported scales.
     }
   }
 }
 
 } // namespace