Initial ResizeObserver implementation

third_party/WebKit/Source/core/dom/Element.h

Index: third_party/WebKit/Source/core/dom/Element.h
diff --git a/third_party/WebKit/Source/core/dom/Element.h b/third_party/WebKit/Source/core/dom/Element.h
index 02be63d7fcecb0c4f69fd3a294d009132a6354e8..b632ce1185aad0df17a386ac884fd96a66cdb776 100644
--- a/third_party/WebKit/Source/core/dom/Element.h
+++ b/third_party/WebKit/Source/core/dom/Element.h
@@ -63,6 +63,7 @@ class MutableStylePropertySet;
 class NodeIntersectionObserverData;
 class PropertySetCSSStyleDeclaration;
 class PseudoElement;
+class ResizeObservationSet;
 class ScrollState;
 class ScrollStateCallback;
 class ScrollToOptions;
@@ -577,6 +578,8 @@ public:
     NodeIntersectionObserverData* intersectionObserverData() const;
     NodeIntersectionObserverData& ensureIntersectionObserverData();
 
+    ResizeObservationSet& ensureResizeObserverData();
+
 protected:
     Element(const QualifiedName& tagName, Document*, ConstructionType);