Reduce CSSProperty's StylePropertyMetadata memory footprint by half when used inside a ImmutableSty…

Source/core/css/CSSComputedStyleDeclaration.cpp

Index: Source/core/css/CSSComputedStyleDeclaration.cpp
diff --git a/Source/core/css/CSSComputedStyleDeclaration.cpp b/Source/core/css/CSSComputedStyleDeclaration.cpp
index 3a91fc73114aa0cac5f01e4761b6c354d3be7721..83ea84604b883ed6df2eb05e58d430f6898773f7 100644
--- a/Source/core/css/CSSComputedStyleDeclaration.cpp
+++ b/Source/core/css/CSSComputedStyleDeclaration.cpp
@@ -2994,8 +2994,8 @@ PassRefPtr<CSSValueList> CSSComputedStyleDeclaration::getBackgroundShorthandValu
                                                                     CSSPropertyBackgroundClip };
 
     RefPtr<CSSValueList> list = CSSValueList::createSlashSeparated();
-    list->append(getCSSPropertyValuesForShorthandProperties(StylePropertyShorthand(propertiesBeforeSlashSeperator, WTF_ARRAY_LENGTH(propertiesBeforeSlashSeperator))));
-    list->append(getCSSPropertyValuesForShorthandProperties(StylePropertyShorthand(propertiesAfterSlashSeperator, WTF_ARRAY_LENGTH(propertiesAfterSlashSeperator))));
+    list->append(getCSSPropertyValuesForShorthandProperties(StylePropertyShorthand(CSSPropertyBackground, propertiesBeforeSlashSeperator, WTF_ARRAY_LENGTH(propertiesBeforeSlashSeperator))));
+    list->append(getCSSPropertyValuesForShorthandProperties(StylePropertyShorthand(CSSPropertyBackground, propertiesAfterSlashSeperator, WTF_ARRAY_LENGTH(propertiesAfterSlashSeperator))));
     return list.release();
 }