IntersectionObserver: second cut.

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

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef IntersectionObserverController_h
+#define IntersectionObserverController_h
+
+#include "core/dom/Element.h"
+#include "core/dom/IntersectionObserver.h"
+#include "platform/Timer.h"
+#include "platform/heap/Handle.h"
+#include "wtf/HashSet.h"
+
+namespace blink {
+
+class IntersectionObserverController : public GarbageCollectedFinalized<IntersectionObserverController> {
+public:
+    IntersectionObserverController();
+    ~IntersectionObserverController();
+
+    void scheduleIntersectionObserverForDelivery(IntersectionObserver&);
+    void resumeSuspendedIntersectionObservers();
+    void deliverIntersectionObservations(Timer<IntersectionObserverController>*);
+    void computeTrackedIntersectionObservations();
+    void addTrackedObserver(IntersectionObserver&);
+    void removeTrackedObserversForRoot(const Element&);
+
+    DECLARE_TRACE();
+
+private:
+    // Design doc for IntersectionObserver implementation:
+    //   https://docs.google.com/a/google.com/document/d/1hLK0eyT5_BzyNS4OkjsnoqqFQDYCbKfyBinj94OnLiQ
+
+    Timer<IntersectionObserverController> m_timer;
+    // IntersectionObservers for which this is the tracking document.
+    HeapHashSet<WeakMember<IntersectionObserver>> m_trackedIntersectionObservers;
+    // IntersectionObservers for which this is the execution context of the callback.
+    HeapHashSet<Member<IntersectionObserver>> m_pendingIntersectionObservers;
+    HeapHashSet<Member<IntersectionObserver>> m_suspendedIntersectionObservers;
+};
+
+} // namespace blink
+
+#endif // IntersectionObserverController_h