workspace: include the close button overlap in the right side chrome

As we do for the top side; the border is overlaied in the top/right
corner.

https://bugzilla.gnome.org/show_bug.cgi?id=682050

js/ui/workspace.js

@@ -524,7 +524,8 @@ const WindowOverlay = new Lang.Class({
     },
 
     chromeWidths: function () {
-        return [this.borderSize, this.borderSize];
+        return [this.borderSize,
+                Math.max(this.borderSize, this.closeButton.width - this.closeButton._overlap)];
     },
 
     relayout: function(animate) {