Delay construction of StyleResolverState until after style sharing.

Source/core/css/resolver/ElementResolveContext.h

Index: Source/core/css/resolver/ElementResolveContext.h
diff --git a/Source/core/css/resolver/ElementResolveContext.h b/Source/core/css/resolver/ElementResolveContext.h
index 09b8cd105c0b09a52401488136873f525f23432d..ae15df57d802745a05566742ccd5a335d8b45d6a 100644
--- a/Source/core/css/resolver/ElementResolveContext.h
+++ b/Source/core/css/resolver/ElementResolveContext.h
@@ -43,6 +43,7 @@ public:
     Element* element() const { return m_element; }
     const ContainerNode* parentNode() const { return m_parentNode; }
     const RenderStyle* rootElementStyle() const { return m_rootElementStyle; }
+    RenderStyle* parentStyle() const { return parentNode() ? parentNode()->renderStyle() : nullptr; }
     EInsideLink elementLinkState() const { return m_elementLinkState; }
     bool distributedToInsertionPoint() const { return m_distributedToInsertionPoint; }