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

Source/core/css/CSSProperty.cpp

Index: Source/core/css/CSSProperty.cpp
diff --git a/Source/core/css/CSSProperty.cpp b/Source/core/css/CSSProperty.cpp
index d9d0f2afe400d8ea94bf392a35047e465313c3e4..b9e59a50f45729a1462bdf65d0febaf01029a17e 100644
--- a/Source/core/css/CSSProperty.cpp
+++ b/Source/core/css/CSSProperty.cpp
@@ -37,6 +37,20 @@ struct SameSizeAsCSSProperty {
 
 COMPILE_ASSERT(sizeof(CSSProperty) == sizeof(SameSizeAsCSSProperty), CSSProperty_should_stay_small);
 
+CSSPropertyID StylePropertyMetadata::shorthandID() const
+{
+    if (!m_isSetFromShorthand)
+        return CSSPropertyInvalid;
+
+    const Vector<StylePropertyShorthand> shorthands = matchingShorthandsForLonghand(static_cast<CSSPropertyID>(m_propertyID));
+    ASSERT(shorthands.size());
+    if (shorthands.size() > 1) {
+        ASSERT(m_shorthandID >= 0 && m_shorthandID < shorthands.size());
+        return shorthands.at(m_shorthandID).id();
+    }
+    return shorthands.at(0).id();
+}
+
 void CSSProperty::wrapValueInCommaSeparatedList()
 {
     RefPtr<CSSValue> value = m_value.release();
@@ -164,7 +178,7 @@ static CSSPropertyID resolveToPhysicalProperty(WritingMode writingMode, LogicalE
 static const StylePropertyShorthand& borderDirections()
 {
     static const CSSPropertyID properties[4] = { CSSPropertyBorderTop, CSSPropertyBorderRight, CSSPropertyBorderBottom, CSSPropertyBorderLeft };
-    DEFINE_STATIC_LOCAL(StylePropertyShorthand, borderDirections, (properties, WTF_ARRAY_LENGTH(properties)));
+    DEFINE_STATIC_LOCAL(StylePropertyShorthand, borderDirections, (CSSPropertyBorder, properties, WTF_ARRAY_LENGTH(properties)));
     return borderDirections;
 }