ResizeObserver pt5: size change notification

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"
 #include "core/svg/SVGElement.h"
 #include "core/svg/SVGGraphicsElement.h"
 
 namespace blink {
 
 ResizeObservation::ResizeObservation(Element* target, ResizeObserver* observer)
     : m_target(target)
     , m_observer(observer)
     , m_observationSize(0, 0)
+    , m_elementSizeChanged(true)
 {
     DCHECK(m_target);
+    m_observer->elementSizeChanged();
 }
 
 void ResizeObservation::setObservationSize(const LayoutSize& size)
 {
     m_observationSize = size;
+    m_elementSizeChanged = false;
 }
 
 bool ResizeObservation::observationSizeOutOfSync() const
 {
-    return m_observationSize != ResizeObservation::getTargetSize(m_target);
+    return m_elementSizeChanged && m_observationSize != ResizeObservation::getTargetSize(m_target);
 }
 
 size_t ResizeObservation::targetDepth()
 {
     unsigned depth = 0;
     for (Element* parent = m_target; parent; parent = parent->parentElement())
         ++depth;
     return depth;
 }
 
 LayoutSize ResizeObservation::getTargetSize(Element* target) // static
 {
     if (target) {
         if (target->isSVGElement() && toSVGElement(target)->isSVGGraphicsElement()) {
             SVGGraphicsElement& svg = toSVGGraphicsElement(*target);
             return LayoutSize(svg.getBBox().size());
         }
         LayoutBox* layout = target->layoutBox();
         if (layout)
             return layout->contentSize();
     }
     return LayoutSize();
 }
 
+void ResizeObservation::elementSizeChanged()
+{
+    m_elementSizeChanged = true;
+    m_observer->elementSizeChanged();
+}
 
 DEFINE_TRACE(ResizeObservation)
 {
     visitor->trace(m_target);
     visitor->trace(m_observer);
 }
 
 } // namespace blink