IntersectionObserver: second cut.

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

Index: third_party/WebKit/Source/core/dom/ElementRareData.h
diff --git a/third_party/WebKit/Source/core/dom/ElementRareData.h b/third_party/WebKit/Source/core/dom/ElementRareData.h
index 5e27cfe6ef0a797ef74015199dba900aba584b20..dec5fd7f16706b30ef62d05d4aa80c1c95f3a190 100644
--- a/third_party/WebKit/Source/core/dom/ElementRareData.h
+++ b/third_party/WebKit/Source/core/dom/ElementRareData.h
@@ -25,6 +25,8 @@
 #include "core/animation/ElementAnimations.h"
 #include "core/dom/Attr.h"
 #include "core/dom/DatasetDOMStringMap.h"
+#include "core/dom/IntersectionObservation.h"
+#include "core/dom/IntersectionObserver.h"
 #include "core/dom/NamedNodeMap.h"
 #include "core/dom/NodeRareData.h"
 #include "core/dom/PseudoElement.h"
@@ -33,7 +35,9 @@
 #include "core/html/ClassList.h"
 #include "core/style/StyleInheritedData.h"
 #include "platform/heap/Handle.h"
+#include "wtf/HashSet.h"
 #include "wtf/OwnPtr.h"
+#include "wtf/WeakPtr.h"
 
 namespace blink {
 
@@ -107,6 +111,25 @@ public:
         m_elementAnimations = elementAnimations;
     }
 
+    bool hasIntersectionObservation() const
+    {
+        return m_intersectionObservations && m_intersectionObservations->size();
+    }
+
+    IntersectionObservation::HashSet& intersectionObservations()
+    {
+        if (!m_intersectionObservations)
+            m_intersectionObservations = adoptPtrWillBeNoop(new IntersectionObservation::HashSet());
+        return *m_intersectionObservations.get();
+    }
+
+    WeakPtr<Element> createWeakPtr(Element* element)
+    {
+        if (!m_weakPointerFactory)
+            m_weakPointerFactory = adoptPtrWillBeNoop(new WeakPtrFactory<Element>(element));
+        return m_weakPointerFactory->createWeakPtr();
+    }
+
     bool hasPseudoElements() const;
     void clearPseudoElements();
 
@@ -144,6 +167,11 @@ private:
     PersistentWillBeMember<ElementAnimations> m_elementAnimations;
     OwnPtrWillBeMember<InlineCSSStyleDeclaration> m_cssomWrapper;
 
+    // Note that m_intersectionObservers will contain both observers for which this element is target,
+    // and observers for which this element is root.  To tell them apart, check (observer->root() == element).
+    OwnPtrWillBeMember<IntersectionObservation::HashSet> m_intersectionObservations;
+    OwnPtrWillBeMember<WeakPtrFactory<Element>> m_weakPointerFactory;
+
     RefPtr<ComputedStyle> m_computedStyle;
     RefPtrWillBeMember<CustomElementDefinition> m_customElementDefinition;