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 c055eed195cd1566d7f995128ec2e9e1b667377f..ef0dc0395c9598db7f1633b03b82234e612624a3 100644
--- a/Source/core/css/CSSComputedStyleDeclaration.cpp
+++ b/Source/core/css/CSSComputedStyleDeclaration.cpp
@@ -2998,8 +2998,8 @@ 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();
 }