Add toSVGLengthType() and toSVGLengthMode() fuctions, and use it.

Source/core/svg/SVGLength.cpp

Index: Source/core/svg/SVGLength.cpp
diff --git a/Source/core/svg/SVGLength.cpp b/Source/core/svg/SVGLength.cpp
index f6ae8a77467dae3ddc726d445dbc02d3af8b1ced..0a52ea1fa0f811294900d55d65414f71b76d06f5 100644
--- a/Source/core/svg/SVGLength.cpp
+++ b/Source/core/svg/SVGLength.cpp
@@ -42,14 +42,14 @@ static inline unsigned int storeUnit(SVGLengthMode mode, SVGLengthType type)
 static inline SVGLengthMode extractMode(unsigned int unit)
 {
     unsigned int mode = unit >> 4;
-    return static_cast<SVGLengthMode>(mode);
+    return toSVGLengthMode(mode);
 }
 
 static inline SVGLengthType extractType(unsigned int unit)
 {
     unsigned int mode = unit >> 4;
     unsigned int type = unit ^ (mode << 4);
-    return static_cast<SVGLengthType>(type);
+    return toSVGLengthType(type);
 }
 
 static inline String lengthTypeToString(SVGLengthType type)
@@ -266,7 +266,7 @@ void SVGLength::newValueSpecifiedUnits(unsigned short type, float value, Excepti
         return;
     }
 
-    m_unit = storeUnit(extractMode(m_unit), static_cast<SVGLengthType>(type));
+    m_unit = storeUnit(extractMode(m_unit), toSVGLengthType(type));
     m_valueInSpecifiedUnits = value;
 }
 
@@ -282,7 +282,7 @@ void SVGLength::convertToSpecifiedUnits(unsigned short type, const SVGLengthCont
         return;
 
     unsigned int originalUnitAndType = m_unit;
-    m_unit = storeUnit(extractMode(m_unit), static_cast<SVGLengthType>(type));
+    m_unit = storeUnit(extractMode(m_unit), toSVGLengthType(type));
     setValue(valueInUserUnits, context, es);
     if (!es.hadException())
         return;