Fix warnings

com.unity.shadergraph/Editor/Drawing/Views/MaterialGraphView.cs

             onConvertToSubgraphClick();
         }
 
-        public delegate void OnSelectionChanged(IEnumerable<INode> nodes);
-
-        public OnSelectionChanged onSelectionChanged;
-
-        void SelectionChanged()
-        {
-            var selectedNodes = selection.OfType<MaterialNodeView>().Where(x => x.userData is INode);
-        }
-
-        public override void AddToSelection(ISelectable selectable)
-        {
-            base.AddToSelection(selectable);
-            SelectionChanged();
-        }
-
-        public override void RemoveFromSelection(ISelectable selectable)
-        {
-            base.RemoveFromSelection(selectable);
-            SelectionChanged();
-        }
-
-        public override void ClearSelection()
-        {
-            base.ClearSelection();
-            SelectionChanged();
-        }
-
         string SerializeGraphElementsImplementation(IEnumerable<GraphElement> elements)
         {
             var graph = new CopyPasteGraph(elements.OfType<MaterialNodeView>().Select(x => (INode)x.node), elements.OfType<Edge>().Select(x => x.userData).OfType<IEdge>());

com.unity.shadergraph/Editor/Drawing/Views/MaterialNodeView.cs

         VisualElement m_SettingsButton;
         VisualElement m_Settings;
         VisualElement m_NodeSettingsView;
-        VisualElement m_CollapseButton;
 
 
         public void Initialize(AbstractMaterialNode inNode, PreviewManager previewManager, IEdgeConnectorListener connectorListener)
             }
 
             m_PortInputContainer.SendToBack();
-
-            m_CollapseButton = this.Q("collapse-button");
 
             // Remove this after updated to the correct API call has landed in trunk. ------------
             VisualElement m_TitleContainer;