implement clear() in Image

git-svn-id: http://svn.openlayers.org/trunk/openlayers@1155 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Tile/Image.js

@@ -57,6 +57,13 @@ OpenLayers.Tile.Image.prototype =
         this.layer.div.appendChild(this.imgDiv);
     },
 
+    /** Clear the tile of any bounds/position-related data so that it can 
+     *   be reused in a new location.
+     */
+    clear: function() {
+        this.imgDiv.style.display = "none";
+    },
+
     /** 
      * @param {OpenLayers.Bounds}
      * @param {OpenLayers.pixel} position