Enable strict-virtual-specifiers for iOS builds.

ui/gfx/image/image.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.h"
 
 #include <algorithm>
 #include <set>
 
 #include "base/logging.h"
@@ skipping 270 matching lines @@
 
 #if defined(OS_IOS)
 class ImageRepCocoaTouch : public ImageRep {
  public:
   explicit ImageRepCocoaTouch(UIImage* image)
       : ImageRep(Image::kImageRepCocoaTouch),
         image_(image) {
     CHECK(image);
   }
 
-  virtual ~ImageRepCocoaTouch() {
+  ~ImageRepCocoaTouch() override {
     base::mac::NSObjectRelease(image_);
     image_ = nil;
   }
 
-  virtual int Width() const override {
-    return Size().width();
-  }
+  int Width() const override { return Size().width(); }
 
-  virtual int Height() const override {
-    return Size().height();
-  }
+  int Height() const override { return Size().height(); }
 
-  virtual gfx::Size Size() const override {
-    return internal::UIImageSize(image_);
-  }
+  gfx::Size Size() const override { return internal::UIImageSize(image_); }
 
   UIImage* image() const { return image_; }
 
  private:
   UIImage* image_;
 
   DISALLOW_COPY_AND_ASSIGN(ImageRepCocoaTouch);
 };
 #elif defined(OS_MACOSX)
 class ImageRepCocoa : public ImageRep {
@@ skipping 436 matching lines @@
   }
   return it->second;
 }
 
 void Image::AddRepresentation(internal::ImageRep* rep) const {
   CHECK(storage_.get());
   storage_->representations().insert(std::make_pair(rep->type(), rep));
 }
 
 }  // namespace gfx