Initial ResizeObserver implementation

third_party/WebKit/Source/core/observer/ResizeObserver.h

Index: third_party/WebKit/Source/core/observer/ResizeObserver.h
diff --git a/third_party/WebKit/Source/core/observer/ResizeObserver.h b/third_party/WebKit/Source/core/observer/ResizeObserver.h
new file mode 100644
index 0000000000000000000000000000000000000000..87b1157b11f2d00b94035306ba5a2667386aed82
--- /dev/null
+++ b/third_party/WebKit/Source/core/observer/ResizeObserver.h
@@ -0,0 +1,66 @@
+// 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"

[szager1, 2016/05/23 19:49:11]

I don't think you use this.

+#include "core/dom/Element.h"

[szager1, 2016/05/23 19:49:12]

You shouldn't need this, the forward class declaration is sufficient.

+#include "core/observer/ResizeObserverEntry.h"

[szager1, 2016/05/23 19:49:12]

I don't think you use this.

+#include "platform/heap/Handle.h"
+
+namespace blink {
+
+class Document;
+class Element;
+class ResizeObserverCallback;
+class ResizeObserverEntry;

[szager1, 2016/05/23 19:49:11]

I don't think you use this.

+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() {};

[szager1, 2016/05/23 19:49:12]

No unnecessary destructors, switch class to GarbageCollected<>

+
+    // API methods
+    void observe(Element*);
+    void unobserve(Element*);
+    void disconnect();
+
+    DECLARE_TRACE();
+
+    void gatherObservations();

[szager1, 2016/05/23 19:49:12]

Too much whitespace.

+
+    bool hasObservations() const { return !m_activeObservations.isEmpty(); }
+
+    void deliverObservations();
+
+private:
+
+    // FIXME(atotic): for GC, I need an ordered list of WeakMembers here.
+    using ObservationList = HeapVector<Member<ResizeObservation>>;

[szager1, 2016/05/23 19:49:11]

No typedef's or "using", just use full type everywhere.

Also, should this be HeapVector<WeakMember<ResizeObservation>> ?  If a
ResizeObservation's target Element goes away, the ResizeObserver should not keep
the ResizeObservation alive.

And consider using HashSet rather than Vector, for fast lookup/remove.

+
+    ObservationList::iterator find(Element*);
+
+    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