Enable strict-virtual-specifiers for iOS builds.

ui/gfx/platform_font_ios.h

 // 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.
 
 #ifndef UI_GFX_PLATFORM_FONT_IOS_H_
 #define UI_GFX_PLATFORM_FONT_IOS_H_
 
 #include "ui/gfx/platform_font.h"
 
 namespace gfx {
 
 class PlatformFontIOS : public PlatformFont {
  public:
   PlatformFontIOS();
   explicit PlatformFontIOS(NativeFont native_font);
   PlatformFontIOS(const std::string& font_name,
                   int font_size);
 
   // Overridden from PlatformFont:
-  virtual Font DeriveFont(int size_delta, int style) const override;
-  virtual int GetHeight() const override;
-  virtual int GetBaseline() const override;
-  virtual int GetCapHeight() const override;
-  virtual int GetExpectedTextWidth(int length) const override;
-  virtual int GetStyle() const override;
-  virtual std::string GetFontName() const override;
-  virtual std::string GetActualFontNameForTesting() const override;
-  virtual int GetFontSize() const override;
-  virtual const FontRenderParams& GetFontRenderParams() override;
-  virtual NativeFont GetNativeFont() const override;
+  Font DeriveFont(int size_delta, int style) const override;
+  int GetHeight() const override;
+  int GetBaseline() const override;
+  int GetCapHeight() const override;
+  int GetExpectedTextWidth(int length) const override;
+  int GetStyle() const override;
+  std::string GetFontName() const override;
+  std::string GetActualFontNameForTesting() const override;
+  int GetFontSize() const override;
+  const FontRenderParams& GetFontRenderParams() override;
+  NativeFont GetNativeFont() const override;
 
  private:
   PlatformFontIOS(const std::string& font_name, int font_size, int style);
-  virtual ~PlatformFontIOS() {}
+  ~PlatformFontIOS() override {}
 
   // Initialize the object with the specified parameters.
   void InitWithNameSizeAndStyle(const std::string& font_name,
                                 int font_size,
                                 int style);
 
   // Calculate and cache the font metrics.
   void CalculateMetrics();
 
   std::string font_name_;
   int font_size_;
   int style_;
 
   // Cached metrics, generated at construction.
   int height_;
   int ascent_;
   int cap_height_;
   int average_width_;
 
   DISALLOW_COPY_AND_ASSIGN(PlatformFontIOS);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_PLATFORM_FONT_IOS_H_