Updates subpixel positioning and hinting when DSF is changed

ui/gfx/platform_font_ios.mm

 // 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/platform_font_ios.h"
 
 #import <UIKit/UIKit.h>
 
 #include <cmath>
 
@@ skipping 61 matching lines @@
 }
 
 std::string PlatformFontIOS::GetActualFontNameForTesting() const {
   return base::SysNSStringToUTF8([GetNativeFont() familyName]);
 }
 
 int PlatformFontIOS::GetFontSize() const {
   return font_size_;
 }
 
-const FontRenderParams& PlatformFontIOS::GetFontRenderParams() const {
+const FontRenderParams& PlatformFontIOS::GetFontRenderParams() {
   NOTIMPLEMENTED();
   static FontRenderParams params;
   return params;
 }
 
 NativeFont PlatformFontIOS::GetNativeFont() const {
   return [UIFont fontWithName:base::SysUTF8ToNSString(font_name_)
                          size:font_size_];
 }
 
@@ skipping 36 matching lines @@
   return new PlatformFontIOS(native_font);
 }
 
 // static
 PlatformFont* PlatformFont::CreateFromNameAndSize(const std::string& font_name,
                                                   int font_size) {
   return new PlatformFontIOS(font_name, font_size);
 }
 
 }  // namespace gfx