Initial ResizeObserver implementation

third_party/WebKit/Source/core/observer/ResizeObserver.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 ResizeObserver_h
+#define ResizeObserver_h
+
+#include "bindings/core/v8/ScriptWrappable.h"
+#include "platform/heap/Handle.h"
+
+namespace blink {
+
+class Document;
+class Element;
+class ResizeObserverCallback;
+class ResizeObserverEntry;
+class ResizeObservation;
+
+// ResizeObserver represents ResizeObserver javascript api:
+// https://github.com/WICG/ResizeObserver/
+class ResizeObserver final : public GarbageCollectedFinalized<ResizeObserver>, public ScriptWrappable {
+    DEFINE_WRAPPERTYPEINFO();
+public:
+    static ResizeObserver* create(Document&, ResizeObserverCallback*);
+
+    virtual ~ResizeObserver() {};
+
+    // API methods
+    void observe(Element*);
+    void unobserve(Element*);
+    void disconnect();
+
+    DECLARE_TRACE();
+
+    // returns true if observations were found.
+    bool gatherObservations();
+
+    void deliverObservations();
+
+    void clearObservations();
+
+private:
+
+    using ObservationList = HeapLinkedHashSet<WeakMember<ResizeObservation>>;
+
+    explicit ResizeObserver(ResizeObserverCallback*);
+
+    Member<ResizeObserverCallback> m_callback;
+
+    // List of elements we are observing
+    ObservationList m_observations;
+
+    // List of elements that have changes
+    HeapVector<Member<ResizeObservation>> m_activeObservations;
+
+};
+
+
+} // namespace blink
+
+#endif // ResizeObserver_h