Tile.Image should register for error events with respect to tile loading

events -- this means that if an image fails to load, it will still trigger
a loadend event, and the layer will eventually be in a state where it is no
longer waiting to load. Thanks to Andreas for the investigation! (Closes #842) 


git-svn-id: http://svn.openlayers.org/trunk/openlayers@5428 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Tile/Image.js

@@ -216,6 +216,21 @@ OpenLayers.Tile.Image = OpenLayers.Class(OpenLayers.Tile, {
         OpenLayers.Event.observe(this.imgDiv, 'load',
                                  OpenLayers.Function.bind(onload, this));
 
+        // Bind a listener to the onerror of the image div so that we
+        // can registere when a tile has finished loading with errors.
+        var onerror = function() {
+
+            // If we have gone through all image reload attempts, it is time
+            // to realize that we are done with this image. Since
+            // OpenLayers.Util.onImageLoadError already has taken care about
+            // the error, we can continue as if the image was loaded
+            // successfully.
+            if (this.imgDiv._attempts > OpenLayers.IMAGE_RELOAD_ATTEMPTS) {
+                onload.call(this);
+            }
+        };
+        OpenLayers.Event.observe(this.imgDiv, "error",
+                                 OpenLayers.Function.bind(onerror, this));
     },
 
     /**