Updates subpixel positioning and hinting when DSF is changed

ui/gfx/platform_font_mac.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_mac.h"
 
 #include <Cocoa/Cocoa.h>
 
 #include "base/basictypes.h"
 #include "base/mac/scoped_nsobject.h"
@@ skipping 108 matching lines @@
 }
 
 std::string PlatformFontMac::GetActualFontNameForTesting() const {
   return base::SysNSStringToUTF8([native_font_ familyName]);
 }
 
 int PlatformFontMac::GetFontSize() const {
   return font_size_;
 }
 
-const FontRenderParams& PlatformFontMac::GetFontRenderParams() const {
+const FontRenderParams& PlatformFontMac::GetFontRenderParams() {
   return render_params_;
 }
 
 NativeFont PlatformFontMac::GetNativeFont() const {
   return [[native_font_.get() retain] autorelease];
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // PlatformFontMac, private:
 
@@ skipping 50 matching lines @@
   return new PlatformFontMac(native_font);
 }
 
 // static
 PlatformFont* PlatformFont::CreateFromNameAndSize(const std::string& font_name,
                                                   int font_size) {
   return new PlatformFontMac(font_name, font_size);
 }
 
 }  // namespace gfx