jsfiddle/OpenLayers.debug.js
function() {
        var tileWidth = this.extent.getWidth() / this.map.getResolution();
        var tileHeight = this.extent.getHeight() / this.map.getResolution();
        this.tileSize = new OpenLayers.Size(tileWidth, tileHeight);
    }
function() {
        var tileWidth = this.extent.getWidth() / this.map.getResolution();
        var tileHeight = this.extent.getHeight() / this.map.getResolution();
        this.tileSize = new OpenLayers.Size(tileWidth, tileHeight);
    }
function ( ) { var tileWidth = this . extent . getWidth ( ) / this . map . getResolution ( ) ; var tileHeight = this . extent . getHeight ( ) / this . map . getResolution ( ) ; this . tileSize = new OpenLayers . Size ( tileWidth , tileHeight ) ; }
Set the tile size based on the map size.
Set the tile size based on the map size .