Give content area focus after sidebar is closed using F9.

b  = 78440
r  = timeless@mac.com
sr = alecf@netscape.com

xpfe/components/sidebar/resources/sidebarOverlay.js

@@ -884,6 +884,7 @@ function SidebarShowHide() {
   // Immediately save persistent values
   document.persist('sidebar-title-box', 'hidden');
   persist_width();
+  window._content.focus();
 }
 
 function SidebarBuildPickerPopup() {