Get rid of method setProperty(): never used in the whole code

Source/core/css/StylePropertySet.cpp

Index: Source/core/css/StylePropertySet.cpp
diff --git a/Source/core/css/StylePropertySet.cpp b/Source/core/css/StylePropertySet.cpp
index e916b61fd8f5848ebd51784c4a9285c144679e83..95a21b76e904a07b84b22ee51daba381b6cd6ed3 100644
--- a/Source/core/css/StylePropertySet.cpp
+++ b/Source/core/css/StylePropertySet.cpp
@@ -331,12 +331,6 @@ bool MutableStylePropertySet::setProperty(CSSPropertyID propertyID, CSSValueID i
     return true;
 }
 
-bool MutableStylePropertySet::setProperty(CSSPropertyID propertyID, CSSPropertyID identifier, bool important)
-{
-    setProperty(CSSProperty(propertyID, cssValuePool().createIdentifierValue(identifier), important));
-    return true;
-}
-
 void MutableStylePropertySet::parseDeclaration(const String& styleDeclaration, StyleSheetContents* contextStyleSheet)
 {
     m_propertyVector.clear();