Add clone methods to Tile and Tile.Image, and add associated tests. r=crschmidt (closes #1296)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@5854 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Tile.js

@@ -119,6 +119,30 @@ OpenLayers.Tile = OpenLayers.Class({
         this.events.destroy();
         this.events = null;
     },
+    
+    /**
+     * Method: clone
+     *
+     * Parameters:
+     * obj - {<OpenLayers.Tile>} The tile to be cloned
+     *
+     * Returns:
+     * {<OpenLayers.Tile>} An exact clone of this <OpenLayers.Tile>
+     */
+    clone: function (obj) {
+        if (obj == null) {
+            obj = new OpenLayers.Tile(this.layer, 
+                                      this.position, 
+                                      this.bounds, 
+                                      this.url, 
+                                      this.size);
+        } 
+        
+        // catch any randomly tagged-on properties
+        OpenLayers.Util.applyDefaults(obj, this);
+        
+        return obj;
+    },
 
     /**
      * Method: draw