Modify initSingleTile to respect map or layer maxExtent when set and layer is not the map's baseLayer

lib/OpenLayers/Layer/Grid.js

@@ -718,18 +718,50 @@ OpenLayers.Layer.Grid = OpenLayers.Class(OpenLayers.Layer.HTTPRequest, {
      */
     initSingleTile: function(bounds) {
         this.clearTileQueue();
-
+        //determine if a maxExtent restriction exists
+        var maxExt = this.maxExtent || this.map.getMaxExtent() || this.map.maxExtent;
+        
         //determine new tile bounds
+        var tileWidth, tileHeight, tileBounds;
         var center = bounds.getCenterLonLat();
-        var tileWidth = bounds.getWidth() * this.ratio;
+        //adjust tile bounds to fit in maxExtent restriction
-        var tileHeight = bounds.getHeight() * this.ratio;
+        //if it is an overlay and there is a maxExtent restriction
-                                       
+        if(this != this.map.baseLayer && maxExt && bounds.containsBounds(maxExt)) {
-        var tileBounds = 
+            bounds.bottom = Math.max(maxExt.bottom, bounds.bottom);
-            new OpenLayers.Bounds(center.lon - (tileWidth/2),
+            bounds.top = Math.min(maxExt.top, bounds.top);
-                                  center.lat - (tileHeight/2),
+            bounds.left = Math.max(maxExt.left, bounds.left);
-                                  center.lon + (tileWidth/2),
+            bounds.right = Math.min(maxExt.right, bounds.right);
-                                  center.lat + (tileHeight/2));
+            tileWidth = bounds.getWidth();
-  
+            tileHeight = bounds.getHeight();
+            tileBounds = bounds;
+            var blPx = this.map.getLayerPxFromLonLat({
+                lon : tileBounds.left,
+                lat : tileBounds.bottom
+            });
+            var trPx = this.map.getLayerPxFromLonLat({
+                lon : tileBounds.right,
+                lat : tileBounds.top
+            });
+            this.tileSize = {
+                h : Math.abs(trPx.y - blPx.y),
+                w : Math.abs(trPx.x - blPx.x)
+            };
+            this._resetTileSize = true;
+        }
+        else {
+            tileWidth = bounds.getWidth() * this.ratio;
+            tileHeight = bounds.getHeight() * this.ratio;
+            tileBounds = 
+                new OpenLayers.Bounds(
+                    center.lon - (tileWidth / 2), 
+                    center.lat - (tileHeight / 2), 
+                    center.lon + (tileWidth / 2), 
+                    center.lat + (tileHeight / 2)
+                );
+            if(this._resetTileSize === true) {
+                this.setTileSize();
+            }
+        }
         var px = this.map.getLayerPxFromLonLat({
             lon: tileBounds.left,
             lat: tileBounds.top