Remove FontDescriptionChangeScope, and let FontBuilder partially apply values.

Source/platform/fonts/FontDescription.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Nicholas Shanks <webkit@nickshanks.com>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 71 matching lines @@
         , m_syntheticItalic(false)
         , m_subpixelTextPosition(s_useSubpixelTextPositioning)
         , m_typesettingFeatures(s_defaultTypesettingFeatures)
     {
     }
 
     bool operator==(const FontDescription&) const;
     bool operator!=(const FontDescription& other) const { return !(*this == other); }
 
     struct VariantLigatures {
-        VariantLigatures()
-            : common(NormalLigaturesState)
-            , discretionary(NormalLigaturesState)
-            , historical(NormalLigaturesState)
-            , contextual(NormalLigaturesState)
+        VariantLigatures(LigaturesState state = NormalLigaturesState)
+            : common(state)
+            , discretionary(state)
+            , historical(state)
+            , contextual(state)
         {
         }
 
         unsigned common : 2;
         unsigned discretionary : 2;
         unsigned historical : 2;
         unsigned contextual : 2;
     };
 
     struct Size {
@@ skipping 183 matching lines @@
         && m_script == other.m_script
         && m_syntheticBold == other.m_syntheticBold
         && m_syntheticItalic == other.m_syntheticItalic
         && m_featureSettings == other.m_featureSettings
         && m_subpixelTextPosition == other.m_subpixelTextPosition;
 }
 
 } // namespace blink
 
 #endif