Default the buffer to 0 instead of 2. On small maps (or fullscreen

maps on small devices) this is a huge win: instead of downloading
*42 tiles* on a 500x500 div, we now download just 12, a 3.5x savings
in downloads by default. The buffer of 2 was originally chosen when
most maps were based on slow-loading WMS laeyrs and having an area
to pan into was more important. That default no longer makes sense.

(Closes #3111) r=tschaub


git-svn-id: http://svn.openlayers.org/trunk/openlayers@11481 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

tests/Layer/MapGuide.html

@@ -69,7 +69,7 @@
         layer = new OpenLayers.Layer.MapGuide(name, url, paramsTiled);
         map.addLayer(layer);
         map.setCenter(new OpenLayers.LonLat(0,400000),5);
-        t.eq( layer.grid.length, 6, "Grid rows is correct." );
+        t.eq( layer.grid.length, 3, "Grid rows is correct." );
         // t.eq( layer.grid[0].length, 6, "Grid cols is correct." );
         map.destroy();
     }