Update StyleValue.cssString() to use existing methods instead of rolling our own.

third_party/WebKit/Source/core/css/cssom/SimpleLength.h

 // Copyright 2015 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 SimpleLength_h
 #define SimpleLength_h
 
 #include "bindings/core/v8/ExceptionState.h"
 #include "core/css/cssom/LengthValue.h"
 
@@ skipping 21 matching lines @@
     }
 
     double value() const { return m_value; }
     String unit() const { return LengthValue::lengthTypeToString(m_unit); }
     LengthUnit lengthUnit() const { return m_unit; }
 
     void setValue(double value) { m_value = value; }
 
     StyleValueType type() const override { return StyleValueType::SimpleLengthType; }
 
-    String cssString() const override;
     PassRefPtrWillBeRawPtr<CSSValue> toCSSValue() const override;
 
 protected:
     virtual LengthValue* addInternal(const LengthValue* other, ExceptionState&);
     virtual LengthValue* subtractInternal(const LengthValue* other, ExceptionState&);
     virtual LengthValue* multiplyInternal(double, ExceptionState&);
     virtual LengthValue* divideInternal(double, ExceptionState&);
 
 private:
     SimpleLength(double value, LengthUnit unit) : LengthValue(), m_unit(unit), m_value(value) {}
 
     LengthUnit m_unit;
     double m_value;
 };
 
 #define DEFINE_SIMPLE_LENGTH_TYPE_CASTS(argumentType) \
     DEFINE_TYPE_CASTS(SimpleLength, argumentType, value, \
         value->type() == LengthValue::StyleValueType::SimpleLengthType, \
         value.type() == LengthValue::StyleValueType::SimpleLengthType)
 
 DEFINE_SIMPLE_LENGTH_TYPE_CASTS(LengthValue);
 DEFINE_SIMPLE_LENGTH_TYPE_CASTS(StyleValue);
 
 } // namespace blink
 
 #endif