fix window size issue when scale factor is not 1

Editor/editor/UIWidgetsPanelEditor.cs

 namespace Unity.UIWidgets.Editor {
     [CustomEditor(typeof(UIWidgetsPanel), true)]
     [CanEditMultipleObjects]
-    public class WidgetCanvasEditor : RawImageEditor {
+    public class UIWidgetsPanelEditor : RawImageEditor {
         public override void OnInspectorGUI() {
             base.OnInspectorGUI();
             var pixelRatioProperty = this.serializedObject.FindProperty("devicePixelRatioOverride");

Runtime/engine/UIWidgetsPanel.cs

         }
 
         protected override Vector2 queryWindowSize() {
-            var rect = RectTransformUtility.PixelAdjustRect(this._uiWidgetsPanel.rectTransform,
-                this._uiWidgetsPanel.canvas);
-            var size = new Vector2(rect.width, rect.height) / this._uiWidgetsPanel.devicePixelRatio;
+            var rect = this._uiWidgetsPanel.rectTransform.rect;
+            var size = new Vector2(rect.width,rect.height) * 
+                       this._uiWidgetsPanel.canvas.scaleFactor / this._uiWidgetsPanel.devicePixelRatio;
             size.x = Mathf.Round(size.x);
             size.y = Mathf.Round(size.y);
             return size;