allow user to set the slide factor in keyboarddefauls

git-svn-id: http://svn.openlayers.org/trunk/openlayers@646 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Control/KeyboardDefaults.js

@@ -7,6 +7,9 @@ OpenLayers.Control.KeyboardDefaults = Class.create();
 OpenLayers.Control.KeyboardDefaults.prototype = 
   Object.extend( new OpenLayers.Control(), {
 
+    /** @type int */
+    slideFactor: 50,
+
     /**
      * @constructor
      */
@@ -28,7 +31,7 @@ OpenLayers.Control.KeyboardDefaults.prototype =
     */
     defaultKeyDown: function (evt) {
 
-        var slide = this.getResolution() * 50;
+        var slide = this.getResolution() * this.slideFactor;
         var center = this.getCenter();
     
         var newCenter = center.copyOf();