Make sure tiles are loaded for Bing overlays.

Previously, Bing overlays that were added to an existing map had empty tiles, because tiles are added before the layer url is set in initLayer. This change makes sure tiles are only rendered when the layer url is available, by not processing the tile queue before the layer url is set.

lib/OpenLayers/Layer/Bing.js

@@ -176,6 +176,18 @@ OpenLayers.Layer.Bing = OpenLayers.Class(OpenLayers.Layer.XYZ, {
                 res.zoomMax + 1 - res.zoomMin, this.numZoomLevels
             )
         }, true);
+        this.updateAttribution();
+    },
+
+    /**
+     * Method: drawTileFromQueue
+     * Draws the first tile from the tileQueue, and unqueues that tile
+     */
+    drawTileFromQueue: function() {
+        // don't start working on the queue before we have a url from initLayer
+        if (this.url) {
+            OpenLayers.Layer.XYZ.prototype.drawTileFromQueue.apply(this, arguments);
+        }
     },
 
     /**
@@ -185,9 +197,6 @@ OpenLayers.Layer.Bing = OpenLayers.Class(OpenLayers.Layer.XYZ, {
      * bounds - {<OpenLayers.Bounds>}
      */
     getURL: function(bounds) {
-        if (!this.url) {
-            return;
-        }
         var xyz = this.getXYZ(bounds), x = xyz.x, y = xyz.y, z = xyz.z;
         var quadDigits = [];
         for (var i = z; i > 0; --i) {
@@ -253,7 +262,6 @@ OpenLayers.Layer.Bing = OpenLayers.Class(OpenLayers.Layer.XYZ, {
      */
     setMap: function() {
         OpenLayers.Layer.XYZ.prototype.setMap.apply(this, arguments);
-        this.updateAttribution();
         this.map.events.register("moveend", this, this.updateAttribution);
     },