SVG doesn't recognize ch units.

Source/core/svg/SVGLength.h

 /*
  * Copyright (C) 2004, 2005, 2006, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006 Rob Buis <buis@kde.org>
  *
  * 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
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 40 matching lines @@
     virtual PassRefPtrWillBeRawPtr<SVGPropertyBase> cloneForAnimation(const String&) const override;
 
     SVGLengthType unitType() const { return static_cast<SVGLengthType>(m_unitType); }
     CSSPrimitiveValue::UnitType cssUnitTypeQuirk() const
     {
         if (m_unitType == LengthTypeNumber)
             return CSSPrimitiveValue::UnitType::CSS_PX;
 
         if (m_unitType == LengthTypeREMS)
             return CSSPrimitiveValue::UnitType::CSS_REMS;
+        if (m_unitType == LengthTypeCHS)
+            return CSSPrimitiveValue::UnitType::CSS_CHS;
 
         return static_cast<CSSPrimitiveValue::UnitType>(m_unitType);
     }
     void setUnitType(SVGLengthType);
     SVGLengthMode unitMode() const { return static_cast<SVGLengthMode>(m_unitMode); }
 
     bool operator==(const SVGLength&) const;
     bool operator!=(const SVGLength& other) const { return !operator==(other); }
 
     float value(const SVGLengthContext&) const;
@@ skipping 16 matching lines @@
 
     void newValueSpecifiedUnits(SVGLengthType, float valueInSpecifiedUnits);
     void convertToSpecifiedUnits(SVGLengthType, const SVGLengthContext&);
 
     // Helper functions
     static inline bool isRelativeUnit(SVGLengthType unitType)
     {
         return unitType == LengthTypePercentage
             || unitType == LengthTypeEMS
             || unitType == LengthTypeEXS
-            || unitType == LengthTypeREMS;
+            || unitType == LengthTypeREMS
+            || unitType == LengthTypeCHS;
     }
     inline bool isRelative() const { return isRelativeUnit(unitType()); }
 
     bool isZero() const
     {
         return !m_valueInSpecifiedUnits;
     }
 
     static PassRefPtrWillBeRawPtr<SVGLength> fromCSSPrimitiveValue(CSSPrimitiveValue*);
     static PassRefPtrWillBeRawPtr<CSSPrimitiveValue> toCSSPrimitiveValue(PassRefPtrWillBeRawPtr<SVGLength>);
@@ skipping 19 matching lines @@
 inline PassRefPtrWillBeRawPtr<SVGLength> toSVGLength(PassRefPtrWillBeRawPtr<SVGPropertyBase> passBase)
 {
     RefPtrWillBeRawPtr<SVGPropertyBase> base = passBase;
     ASSERT(base->type() == SVGLength::classType());
     return static_pointer_cast<SVGLength>(base.release());
 }
 
 } // namespace blink
 
 #endif // SVGLength_h