New OpenLayers.CANVAS_SUPPORTED constant

lib/OpenLayers/Renderer/Canvas.js

@@ -110,8 +110,7 @@ OpenLayers.Renderer.Canvas = OpenLayers.Class(OpenLayers.Renderer, {
      * {Boolean} Whether or not the browser supports the renderer class
      */
     supported: function() {
-        var canvas = document.createElement("canvas");
+        return OpenLayers.CANVAS_SUPPORTED;
-        return !!canvas.getContext;
     },    
     
     /**

lib/OpenLayers/Util.js

@@ -1435,6 +1435,15 @@ OpenLayers.IS_GECKO = (function() {
     return ua.indexOf("webkit") == -1 && ua.indexOf("gecko") != -1;
 })();
 
+/**
+ * Constant: CANVAS_SUPPORTED
+ * {Boolean} True if canvas 2d is supported.
+ */
+OpenLayers.CANVAS_SUPPORTED = (function() {
+    var elem = document.createElement('canvas');
+    return !!(elem.getContext && elem.getContext('2d'));
+})();
+
 /**
  * Constant: BROWSER_NAME
  * {String}