adds method to gather image asset file names

lib/carto/renderer_js.js

@@ -5,6 +5,7 @@ var _ = global._ || require('underscore');
 
 function CartoCSS(style, options) {
   this.options = options || {};
+  this.imageURLs = [];
   if(style) {
     this.setStyle(style);
   }
@@ -164,6 +165,9 @@ CartoCSS.prototype = {
         }
     }
   },
+  getIconURLs: function(){
+    return this.imageURLs;
+  },
 
   parse: function(cartocss) {
     var parse_env = {
@@ -198,6 +202,13 @@ CartoCSS.prototype = {
         var layer = layers[key] = (layers[key] || {
           symbolizers: []
         });
+        this.imageURLs = _getImageURLs(def);
+        for(var u = 0; u<def.rules.length; u++){
+            if(def.rules[u].name == "marker-file" || def.rules[u].name == "point-file"){
+                var value = def.rules[u].value.value[0].value[0].value.value;
+                this.imageURLs.push(value);
+            }
+        } 
         layer.frames = [];
         layer.zoom = tree.Zoom.all;
         var props = def.toJS(parse_env);