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

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

Index: third_party/WebKit/Source/core/css/resolver/StyleResolverState.h
diff --git a/third_party/WebKit/Source/core/css/resolver/StyleResolverState.h b/third_party/WebKit/Source/core/css/resolver/StyleResolverState.h
index f81711704b1f1a135f13223399229f40246de861..69762ecf69bae444964608845d9f7078b02da3ee 100644
--- a/third_party/WebKit/Source/core/css/resolver/StyleResolverState.h
+++ b/third_party/WebKit/Source/core/css/resolver/StyleResolverState.h
@@ -160,6 +160,9 @@ public:
     void setCustomPropertySetForApplyAtRule(const String&, StylePropertySet*);
     StylePropertySet* customPropertySetForApplyAtRule(const String&);
 
+    void setCssValueForLonghandPropertyId(CSSPropertyID, const CSSValue*);

[Timothy Loh, 2016/06/22 00:06:12]

Css -> CSS

[Andy Mutton, 2016/06/24 04:53:26]

Blurgh! Done.

+    const CSSValue* cssValueForLonghandPropertyId(CSSPropertyID);
+
 private:
     ElementResolveContext m_elementContext;
     Member<Document> m_document;
@@ -186,6 +189,8 @@ private:
     ElementStyleResources m_elementStyleResources;
 
     HeapHashMap<String, Member<StylePropertySet>> m_customPropertySetsForApplyAtRule;
+
+    HeapHashMap<CSSPropertyID, Member<const CSSValue>> m_parsedLonghandCssValueForVariableResolver;

[Timothy Loh, 2016/06/22 00:06:12]

I think this is insufficient for cases like:

$0.style.cssText = '--b1: 10px solid grey; --b2: 20px dashed green; border:
var(--b1); border-right: var(--b2);'

Firefox correctly renders (grey border, green dashed for right border), but I
think we'll get this wrong with this patch.

[Andy Mutton, 2016/06/24 04:53:26]

Done. Weird, more complicated caching structure added. Happy to change any bits
of it that look funky!

 };
 
 } // namespace blink