make transparent wms layers be overlays again. fix test.

git-svn-id: http://svn.openlayers.org/trunk/openlayers@1209 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer/WMS.js

@@ -21,13 +21,8 @@ OpenLayers.Layer.WMS.prototype =
                       format: "image/jpeg"
                      },
 
-    /** WMS layer by default is a base layer. 
-     *   If the user wishes to use a WMS as a datalayer, s/he needs only 
-     *   set this property to false.
-     * 
-     * @type Boolean
-     */
-    isBaseLayer: true,
+    /** @type Boolean */
+    isBaseLayer: null,
 
     /**
     * @constructor
@@ -52,6 +47,8 @@ OpenLayers.Layer.WMS.prototype =
                            OpenLayers.Util.upperCaseObject(this.DEFAULT_PARAMS)
                            );
         }
+        
+        this.isBaseLayer = (this.params.TRANSPARENT != "true");
     },    
 
     /**