Defaults for featureDx and xOffset.

This is mostly done to make SVG and VML tests pass again, but it may also help existing applications that override setExtent or drawFeature without calling the superclass methods properly.

lib/OpenLayers/Renderer/Elements.js

@@ -384,6 +384,7 @@ OpenLayers.Renderer.Elements = OpenLayers.Class(OpenLayers.Renderer, {
      * exceeding the world bounds on the left, we need this offset to make sure
      * that the same is true for the renderer extent in pixel space as well.
      */
+    xOffset: 0,
     
     /**
      * Property: rightOfDateLine