Update DoRepaint for UIElements change in trunk

ShaderGraph/com.unity.shadergraph/Editor/Drawing/Blackboard/BlackboardFieldPropertyView.cs

                         return;
                     colorProperty.colorMode = (ColorMode)evt.newValue;
                     colorField.hdr = colorProperty.colorMode == ColorMode.HDR;
-                    colorField.DoRepaint();
+                    colorField.MarkDirtyRepaint();
                     DirtyNodes();
                 });
                 AddRow("Mode", colorModeField);

ShaderGraph/com.unity.shadergraph/Editor/Drawing/Manipulators/ResizeSideHandle.cs

-using System;
+using System;
 using UnityEngine;
 using UnityEngine.Experimental.UIElements;
 using UnityEngine.Experimental.UIElements.StyleSheets;
             m_WindowDockingLayout.ApplyPosition(m_Container);
         }
 
+#if UNITY_2018_3_OR_NEWER
+        protected override void DoRepaint(IStylePainter painter)
+#else
+#endif
         {
             if (m_StyleWidget == null)
             {