handleBrowserEvent: don't compute mouse position if it's not needed. r=erilem (closes #2880)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@10873 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Events.js

@@ -786,10 +786,15 @@ OpenLayers.Events = OpenLayers.Class({
      * evt - {Event} 
      */
     handleBrowserEvent: function (evt) {
+        var type = evt.type, listeners = this.listeners[type];
+        if(!listeners || listeners.length == 0) {
+            // none's listening, bail out
+            return;
+        }
         if (this.includeXY) {
             evt.xy = this.getMousePosition(evt);
         } 
-        this.triggerEvent(evt.type, evt);
+        this.triggerEvent(type, evt);
     },
 
     /**