add an option to OpenLayers.Strategy.BBOX to allow not aborting previous requests

lib/OpenLayers/Strategy/BBOX.js

@@ -124,9 +124,12 @@ OpenLayers.Strategy.BBOX = OpenLayers.Class(OpenLayers.Strategy, {
      * Callback function called on "moveend" or "refresh" layer events.
      *
      * Parameters:
-     * options - {Object} An object with a property named "force", this
-     *      property references a boolean value indicating if new data
-     *      must be incondtionally read.
+     * options - {Object} Optional object whose properties will determine
+     *     the behaviour of this Strategy
+     *
+     * Valid options include:
+     * force - {Boolean} if true, new data must be unconditionally read.
+     * noAbort - {Boolean} if true, do not abort previous requests.
      */
     update: function(options) {
         var mapBounds = this.getMapBounds();
@@ -218,7 +221,7 @@ OpenLayers.Strategy.BBOX = OpenLayers.Class(OpenLayers.Strategy, {
      *      returned by the layer protocol.
      */
     triggerRead: function(options) {
-        if (this.response) {
+        if (this.response && options.noAbort !== true) {
             this.layer.protocol.abort(this.response);
             this.layer.events.triggerEvent("loadend");
         }