Initial ResizeObserver implementation

third_party/WebKit/Source/core/dom/ElementRareData.cpp

Index: third_party/WebKit/Source/core/dom/ElementRareData.cpp
diff --git a/third_party/WebKit/Source/core/dom/ElementRareData.cpp b/third_party/WebKit/Source/core/dom/ElementRareData.cpp
index 4946f9c3ea78ec4acd838a91701ae1279f3c2420..28881b95cd8cad8fa6e56d3d61c1fc5d967704c0 100644
--- a/third_party/WebKit/Source/core/dom/ElementRareData.cpp
+++ b/third_party/WebKit/Source/core/dom/ElementRareData.cpp
@@ -41,7 +41,7 @@ struct SameSizeAsElementRareData : NodeRareData {
     LayoutSize sizeForResizing;
     IntSize scrollOffset;
     void* pointers[10];
-    Member<void*> persistentMember[3];
+    Member<void*> persistentMember[4];
 };
 
 CSSStyleDeclaration& ElementRareData::ensureInlineCSSStyleDeclaration(Element* ownerElement)
@@ -66,6 +66,13 @@ AttrNodeList& ElementRareData::ensureAttrNodeList()
     return *m_attrNodeList;
 }
 
+ResizeObservationSet& ElementRareData::ensureResizeObserverData()
+{
+    if (!m_resizeObserverData)
+        m_resizeObserverData = new ResizeObservationSet();
+    return *m_resizeObserverData;
+}
+
 DEFINE_TRACE_AFTER_DISPATCH(ElementRareData)
 {
     visitor->trace(m_dataset);
@@ -79,6 +86,7 @@ DEFINE_TRACE_AFTER_DISPATCH(ElementRareData)
     visitor->trace(m_pseudoElementData);
     visitor->trace(m_customElementDefinition);
     visitor->trace(m_intersectionObserverData);
+    visitor->trace(m_resizeObserverData);
     NodeRareData::traceAfterDispatch(visitor);
 }