Remove some dead code from css/ folder

Source/core/css/parser/CSSPropertyParser.h

Index: Source/core/css/parser/CSSPropertyParser.h
diff --git a/Source/core/css/parser/CSSPropertyParser.h b/Source/core/css/parser/CSSPropertyParser.h
index da506b3930f0503828e67020ec80bd2a9eea46a9..b672bc553e9dd2d4dfe0e699f80e947cb183143a 100644
--- a/Source/core/css/parser/CSSPropertyParser.h
+++ b/Source/core/css/parser/CSSPropertyParser.h
@@ -240,9 +240,6 @@ private:
     PassRefPtrWillBeRawPtr<CSSValueList> parseFilter();
     PassRefPtrWillBeRawPtr<CSSFilterValue> parseBuiltinFilterArguments(CSSParserValueList*, CSSFilterValue::FilterOperationType);
 
-    static bool isBlendMode(CSSValueID);
-    static bool isCompositeOperator(CSSValueID);
-
     PassRefPtrWillBeRawPtr<CSSValueList> parseTransformOrigin();
     PassRefPtrWillBeRawPtr<CSSValueList> parseTransform(CSSPropertyID);
     PassRefPtrWillBeRawPtr<CSSValue> parseTransformValue(CSSPropertyID, CSSParserValue*);