make Layer.redraw not unconditionally set zoomChanged to true in moveTo

lib/OpenLayers/Layer.js

@@ -541,7 +541,9 @@ OpenLayers.Layer = OpenLayers.Class({
      * Returns:
      * {Boolean} The layer was redrawn.
      */
-    redraw: function() {
+    redraw: function(zoomChanged) {
+        // zoomChanged forces a zoom change in the layer's moveTo
+        // call. This isn't documented because not part of the API.
         var redrawn = false;
         if (this.map) {
 
@@ -552,7 +554,9 @@ OpenLayers.Layer = OpenLayers.Class({
             var extent = this.getExtent();
 
             if (extent && this.inRange && this.visibility) {
-                var zoomChanged = true;
+                zoomChanged = zoomChanged ||
+                              this._resolution === undefined ||
+                              this._resolution !== this.map.getResolution();
                 this.moveTo(extent, zoomChanged, false);
                 this.events.triggerEvent("moveend",
                     {"zoomChanged": zoomChanged});
@@ -577,6 +581,7 @@ OpenLayers.Layer = OpenLayers.Class({
             display = display && this.inRange;
         }
         this.display(display);
+        this._resolution = this.map.getResolution();
     },
 
     /**
@@ -632,6 +637,8 @@ OpenLayers.Layer = OpenLayers.Class({
             
             // deal with gutters
             this.setTileSize();
+
+            delete this._resolution;
         }
     },