Stash ComputedStyles on new HeapHashMap on Document.

third_party/WebKit/Source/core/dom/Document.h

Index: third_party/WebKit/Source/core/dom/Document.h
diff --git a/third_party/WebKit/Source/core/dom/Document.h b/third_party/WebKit/Source/core/dom/Document.h
index bf6b2ec2e7cc0b3d9532c6c99dcda7366683bb39..73d2206ed994c98e763aefd8098fdf0d8bef0736 100644
--- a/third_party/WebKit/Source/core/dom/Document.h
+++ b/third_party/WebKit/Source/core/dom/Document.h
@@ -328,6 +328,10 @@ class CORE_EXPORT Document : public ContainerNode,
   Range* caretRangeFromPoint(int x, int y);
   Element* scrollingElement();
 
+  void addNonAttachedStyle(Element*, RefPtr<ComputedStyle>);
+  RefPtr<ComputedStyle> getNonAttachedStyle(Element*);
+  void clear();
+
   String readyState() const;
 
   AtomicString characterSet() const { return Document::encodingName(); }
@@ -1411,6 +1415,10 @@ class CORE_EXPORT Document : public ContainerNode,
   Member<DocumentParser> m_parser;
   Member<ContextFeatures> m_contextFeatures;
 
+  using NonAttachedStyleMap =
+      HeapHashMap<Member<Element>, RefPtr<ComputedStyle>>;
+  NonAttachedStyleMap m_nonAttachedStyle;
+
   bool m_wellFormed;
 
   // Document URLs.