Fixes for previews not updating (#1737)

Added a bool for frame all.
Dirty the nodes after Geometry changed event.

com.unity.shadergraph/CHANGELOG.md

 - You can now copy, paste, and duplicate sub-graph nodes with vector type input ports.
 - The Lightweight PBR subshader now normalizes normal, tangent, and view direction correctly.
 - Shader graphs using alpha clip now generate correct depth and shadow passes.
+- `Normal Create` node has been renamed to `Normal From Texture`.
+- The preview of nodes now updates correctly.

com.unity.shadergraph/Editor/Drawing/MaterialGraphEditWindow.cs

 
         ColorSpace m_ColorSpace;
         RenderPipelineAsset m_RenderPipelineAsset;
+        bool m_FrameAllAfterLayout;
 
         GraphEditorView m_GraphEditorView;
 
                     m_GraphEditorView.saveRequested += UpdateAsset;
                     m_GraphEditorView.convertToSubgraphRequested += ToSubGraph;
                     m_GraphEditorView.showInProjectRequested += PingAsset;
+                    m_GraphEditorView.RegisterCallback<GeometryChangedEvent>(OnGeometryChanged);
                     this.GetRootVisualContainer().Add(graphEditorView);
                 }
             }
                     persistenceKey = selectedGuid,
                     assetName = asset.name.Split('/').Last()
                 };
+                m_FrameAllAfterLayout = true;
                 graphEditorView.RegisterCallback<GeometryChangedEvent>(OnGeometryChanged);
 
                 titleContent = new GUIContent(asset.name.Split('/').Last());
         void OnGeometryChanged(GeometryChangedEvent evt)
         {
             graphEditorView.UnregisterCallback<GeometryChangedEvent>(OnGeometryChanged);
-            graphEditorView.graphView.FrameAll();
+            if (m_FrameAllAfterLayout)
+                graphEditorView.graphView.FrameAll();
+            m_FrameAllAfterLayout = false;
+            foreach (var node in m_GraphObject.graph.GetNodes<AbstractMaterialNode>())
+                node.Dirty(ModificationScope.Node);
         }
     }
 }