Add smooth interpolation support for <color> custom properties

third_party/WebKit/Source/core/css/CSSSyntaxDescriptor.h

 // Copyright 2016 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 CSSSyntaxDescriptor_h
 #define CSSSyntaxDescriptor_h
 
+#include "core/animation/InterpolationTypesMap.h"
 #include "core/css/parser/CSSParserTokenRange.h"
 
 namespace blink {
 
 class CSSValue;
 
 enum class CSSSyntaxType {
   TokenStream,
   Ident,
   Length,
@@ skipping 24 matching lines @@
  public:
   CSSSyntaxDescriptor(String syntax);
 
   const CSSValue* parse(CSSParserTokenRange, bool isAnimationTainted) const;
   bool isValid() const { return !m_syntaxComponents.isEmpty(); }
   bool isTokenStream() const {
     return m_syntaxComponents.size() == 1 &&
            m_syntaxComponents[0].m_type == CSSSyntaxType::TokenStream;
   }
 
+  InterpolationTypes createInterpolationTypes(
+      const AtomicString& propertyName) const;
+
  private:
   Vector<CSSSyntaxComponent> m_syntaxComponents;
 };
 
 }  // namespace blink
 
 #endif  // CSSSyntaxDescriptor_h