Recreate windows preview whenever the popup is open.

This ensure previews aspect ratio is correct when windows are resized
after their preview is first created (first time the menu is open).

Author: micheleg

windowPreview.js

@@ -59,13 +59,13 @@ const WindowPreviewMenu = new Lang.Class({
         this._arrowSide = side;
         this._boxPointer._arrowSide = side;
         this._boxPointer._userArrowSide = side;
-
-        this._previewBox = new WindowPreviewList(this._source, this._dtdSettings);
-        this.addMenuItem(this._previewBox);
     },
 
     _redisplay: function() {
-        this._previewBox._shownInitially = false;
+        if (this._previewBox)
+            this._previewBox.destroy();
+        this._previewBox = new WindowPreviewList(this._source, this._dtdSettings);
+        this.addMenuItem(this._previewBox);
         this._previewBox._redisplay();
     },