CSSParser should return ImmutableStylePropertySets.

Source/core/css/CSSParser.h

Index: Source/core/css/CSSParser.h
diff --git a/Source/core/css/CSSParser.h b/Source/core/css/CSSParser.h
index 58876a3a8fb3c9930f65db226358d15f7e5bbebe..428dae913f3300e9fd84493dce7635d986edd86d 100644
--- a/Source/core/css/CSSParser.h
+++ b/Source/core/css/CSSParser.h
@@ -52,6 +52,7 @@ class CSSValueList;
 class CSSBasicShape;
 class Document;
 class Element;
+class ImmutableStylePropertySet;
 class MediaQueryExp;
 class MediaQuerySet;
 class StyleKeyframe;
@@ -98,7 +99,7 @@ public:
     static PassRefPtr<CSSValueList> parseFontFaceValue(const AtomicString&);
     PassRefPtr<CSSPrimitiveValue> parseValidPrimitive(int ident, CSSParserValue*);
     bool parseDeclaration(StylePropertySet*, const String&, SourceDataHandler*, StyleSheetContents* contextStyleSheet);
-    static PassRefPtr<StylePropertySet> parseInlineStyleDeclaration(const String&, Element*);
+    static PassRefPtr<ImmutableStylePropertySet> parseInlineStyleDeclaration(const String&, Element*);
     PassOwnPtr<MediaQuery> parseMediaQuery(const String&);
 
     void addPropertyWithPrefixingVariant(CSSPropertyID, PassRefPtr<CSSValue>, bool important, bool implicit = false);
@@ -344,7 +345,7 @@ public:
 
     void clearProperties();
 
-    PassRefPtr<StylePropertySet> createStylePropertySet();
+    PassRefPtr<ImmutableStylePropertySet> createStylePropertySet();
 
     CSSParserContext m_context;
 
@@ -531,7 +532,7 @@ private:
     bool parseGeneratedImage(CSSParserValueList*, RefPtr<CSSValue>&);
 
     bool parseValue(StylePropertySet*, CSSPropertyID, const String&, bool important, StyleSheetContents* contextStyleSheet);
-    PassRefPtr<StylePropertySet> parseDeclaration(const String&, StyleSheetContents* contextStyleSheet);
+    PassRefPtr<ImmutableStylePropertySet> parseDeclaration(const String&, StyleSheetContents* contextStyleSheet);
 
     enum SizeParameterType {
         None,