Increase priority of region-updating idle

Increase the priority of the idle for updating work area and struts
to META_PRIORITY_BEFORE_REDRAW. This prevents it from being starved
by a constantly-redrawing client.

http://bugzilla.gnome.org/show_bug.cgi?id=585500

js/ui/chrome.js

@@ -231,7 +231,8 @@ Chrome.prototype = {
 
     _queueUpdateRegions: function() {
         if (!this._updateRegionIdle)
-            this._updateRegionIdle = Mainloop.idle_add(Lang.bind(this, this._updateRegions));
+            this._updateRegionIdle = Mainloop.idle_add(Lang.bind(this, this._updateRegions),
+                                                       Meta.PRIORITY_BEFORE_REDRAW);
     },
 
     _windowsRestacked: function() {