IntersectionObserver: second cut.

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

Index: third_party/WebKit/Source/core/dom/Element.h
diff --git a/third_party/WebKit/Source/core/dom/Element.h b/third_party/WebKit/Source/core/dom/Element.h
index 3226de50f813870b89433d27506dbdecfb13ded2..4a28407f71921b40992e04297015026f19bc790a 100644
--- a/third_party/WebKit/Source/core/dom/Element.h
+++ b/third_party/WebKit/Source/core/dom/Element.h
@@ -52,6 +52,7 @@ class CustomElementDefinition;
 class DOMStringMap;
 class DOMTokenList;
 class Dictionary;
+class ElementIntersectionObserverData;
 class ElementRareData;
 class ElementShadow;
 class ExceptionState;
@@ -553,6 +554,9 @@ public:
 
     SpellcheckAttributeState spellcheckAttributeState() const;
 
+    bool hasIntersectionObserverData() const;

[esprehn, 2015/12/22 07:50:32]

Yeah, if you make this be two methods:

* intersectionObserverData();
& ensureIntersectionObserverData();

then callers pick the "could be missing" or "always have one, create if you
must" paths.

+    ElementIntersectionObserverData& ensureIntersectionObserverData();
+
 protected:
     Element(const QualifiedName& tagName, Document*, ConstructionType);