IntersectionObserver: second cut.

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

Index: third_party/WebKit/Source/core/dom/IntersectionObserver.h
diff --git a/third_party/WebKit/Source/core/dom/IntersectionObserver.h b/third_party/WebKit/Source/core/dom/IntersectionObserver.h
new file mode 100644
index 0000000000000000000000000000000000000000..34a89d2615172d6f5baee6413d314695c37434e9
--- /dev/null
+++ b/third_party/WebKit/Source/core/dom/IntersectionObserver.h
@@ -0,0 +1,62 @@
+// 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 IntersectionObserver_h
+#define IntersectionObserver_h
+
+#include "bindings/core/v8/ScriptWrappable.h"
+#include "core/dom/Element.h"
+#include "core/dom/IntersectionObservation.h"
+#include "core/dom/IntersectionObserverEntry.h"
+#include "platform/heap/Handle.h"
+#include "wtf/HashSet.h"
+#include "wtf/RefCounted.h"
+#include "wtf/Vector.h"
+
+namespace blink {
+
+class ExceptionState;
+class IntersectionObserverCallback;
+class IntersectionObserverInit;
+
+class IntersectionObserver final : public GarbageCollectedFinalized<IntersectionObserver>, public ScriptWrappable {
+    DEFINE_WRAPPERTYPEINFO();
+
+public:
+    static IntersectionObserver* create(const IntersectionObserverInit&, IntersectionObserverCallback&, ExceptionState&);
+    static void resumeSuspendedObservers();
+
+    // API methods
+    void observe(Element*, ExceptionState&);
+    void unobserve(Element*, ExceptionState&);
+    HeapVector<Member<IntersectionObserverEntry>> takeRecords();
+
+    Element* root() { return m_root.get(); }
+    LayoutObject* rootLayoutObject();
+    bool isDescendantOfRoot(const Element*) const;
+    void computeIntersectionObservations(double timestamp);
+    void enqueueIntersectionObserverEntry(IntersectionObserverEntry&);
+    unsigned firstThresholdGreaterThan(float ratio) const;
+    void deliver();
+    void setActive(bool);
+    void disconnect();
+    void removeObservation(IntersectionObservation&);
+
+    DECLARE_TRACE();
+
+private:
+    explicit IntersectionObserver(IntersectionObserverCallback&, Element&, const Vector<float>& thresholds);
+
+    void checkRootAndDetachIfNeeded();
+
+    Member<IntersectionObserverCallback> m_callback;
+    WeakPtrWillBeWeakMember<Element> m_root;
+    HeapHashSet<WeakMember<IntersectionObservation>> m_observations;
+    HeapVector<Member<IntersectionObserverEntry>> m_entries;
+    Vector<float> m_thresholds;
+};
+
+} // namespace blink
+
+#endif // IntersectionObserver_h