Initial ResizeObserver implementation

third_party/WebKit/Source/core/observer/ResizeObservation.cpp

+// 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.
+
+#include "core/observer/ResizeObservation.h"
+
+#include "core/layout/LayoutBox.h"
+#include "core/observer/ResizeObserver.h"
+
+namespace blink {
+
+ResizeObservation::ResizeObservation(Element* target, ResizeObserver* observer)
+    : m_target(target)
+    , m_observer(observer)
+    , m_broadcastSize(0, 0)
+{
+    DCHECK(m_target);
+    m_target->ensureResizeObserverData().set(observer, this);
+}
+
+bool ResizeObservation::hasResized() const
+{
+    if (!m_target)
+        return false;
+    LayoutBox* layout = m_target->layoutBox();
+    if (layout)
+        return layout->contentSize() != m_broadcastSize;
+    // else treat no layout as an empty rect.
+    return !m_broadcastSize.isEmpty();
+}
+
+DEFINE_TRACE(ResizeObservation)
+{
+    visitor->trace(m_target);
+    visitor->trace(m_observer);
+}
+
+
+} // namespace blink