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

Source/core/css/StylePropertySet.cpp

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2011 Research In Motion Limited. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 240 matching lines @@
         CSSProperty* toReplace = slot ? slot : findCSSPropertyWithID(property.id());
         if (toReplace) {
             *toReplace = property;
             setPrefixingVariantProperty(property);
             return;
         }
     }
     appendPrefixingVariantProperty(property);
 }
 
+unsigned getShorthandIDForPrefixingVariant(const CSSProperty& property, CSSPropertyID prefixingVariant)
+{
+    unsigned shorthandID = 0;
+    if (property.isSetFromShorthand()) {
+        CSSPropertyID prefixedShorthand = prefixingVariantForPropertyId(property.shorthandID());
+        shorthandID = indexOfShorthandForLonghand(prefixedShorthand, matchingShorthandsForLonghand(prefixingVariant));
+    }
+    return 0;
+}
+
 void MutableStylePropertySet::appendPrefixingVariantProperty(const CSSProperty& property)
 {
     m_propertyVector.append(property);
     CSSPropertyID prefixingVariant = prefixingVariantForPropertyId(property.id());
     if (prefixingVariant == property.id())
         return;
-    m_propertyVector.append(CSSProperty(prefixingVariant, property.value(), property.isImportant(), property.shorthandID(), property.metadata().m_implicit));
+
+    m_propertyVector.append(CSSProperty(prefixingVariant, property.value(), property.isImportant(), property.isSetFromShorthand(), getShorthandIDForPrefixingVariant(property, prefixingVariant), property.metadata().m_implicit));
 }
 
 void MutableStylePropertySet::setPrefixingVariantProperty(const CSSProperty& property)
 {
     CSSPropertyID prefixingVariant = prefixingVariantForPropertyId(property.id());
     CSSProperty* toReplace = findCSSPropertyWithID(prefixingVariant);
-    if (toReplace)
-        *toReplace = CSSProperty(prefixingVariant, property.value(), property.isImportant(), property.shorthandID(), property.metadata().m_implicit);
+    if (toReplace && prefixingVariant != property.id())
+        *toReplace = CSSProperty(prefixingVariant, property.value(), property.isImportant(), property.isSetFromShorthand(), getShorthandIDForPrefixingVariant(property, prefixingVariant), property.metadata().m_implicit);
 }
 
 bool MutableStylePropertySet::setProperty(CSSPropertyID propertyID, CSSValueID identifier, bool important)
 {
     setProperty(CSSProperty(propertyID, cssValuePool().createIdentifierValue(identifier), important));
     return true;
 }
 
 bool MutableStylePropertySet::setProperty(CSSPropertyID propertyID, CSSPropertyID identifier, bool important)
 {
@@ skipping 310 matching lines @@
     result.appendLiteral(": ");
     result.append(propertyValue()->cssText());
     if (isImportant())
         result.appendLiteral(" !important");
     result.append(';');
     return result.toString();
 }
 
 
 } // namespace WebCore