Add expansion of shorthands with custom properties to longhands using a pending substition value.

third_party/WebKit/Source/core/css/resolver/StyleResolverState.cpp

Index: third_party/WebKit/Source/core/css/resolver/StyleResolverState.cpp
diff --git a/third_party/WebKit/Source/core/css/resolver/StyleResolverState.cpp b/third_party/WebKit/Source/core/css/resolver/StyleResolverState.cpp
index 6fc6c070d179659be1265f482642ca16d1119922..d141f765986e53d022193141ee645d6732049359 100644
--- a/third_party/WebKit/Source/core/css/resolver/StyleResolverState.cpp
+++ b/third_party/WebKit/Source/core/css/resolver/StyleResolverState.cpp
@@ -86,4 +86,14 @@ StylePropertySet* StyleResolverState::customPropertySetForApplyAtRule(const Stri
     return m_customPropertySetsForApplyAtRule.get(string);
 }
 
+HeapHashMap<CSSPropertyID, Member<const CSSValue>>& StyleResolverState::parsedPropertiesForPendingSubstitution(const CSSPendingSubstitutionValue& value)
+{
+    HeapHashMap<CSSPropertyID, Member<const CSSValue>>* map = m_parsedPropertiesForPendingSubstitution.get(&value);
+    if (!map) {
+        map = new HeapHashMap<CSSPropertyID, Member<const CSSValue>>;
+        m_parsedPropertiesForPendingSubstitution.set(&value, map);
+    }
+    return *map;
+}
+
 } // namespace blink