fixed support3d to reuse transformProp. prefixProperty returns false instead of "" when the property isn't supported at all

js/id/renderer/map.js

@@ -57,15 +57,13 @@ iD.Map = function() {
         support3d = (function() {
             // test for translate3d support. Based on https://gist.github.com/3794226 by lorenzopolidori and webinista
             var el = document.createElement('div'),
-                has3d = false,
-                transform = iD.util.prefix(['webkit', 'ms', 'Moz']) + 'transform';
+                has3d = false;
             document.body.insertBefore(el,null);
-            if (el.style[transform] !== undefined) {
-                el.style[transform] = 'translate3d(1px,1px,1px)';
-                has3d = window.getComputedStyle(el).getPropertyValue(transform);
+            if (el.style[transformProp] !== undefined) {
+                el.style[transformProp] = 'translate3d(1px,1px,1px)';
+                has3d = window.getComputedStyle(el).getPropertyValue(transformProp);
             }
             document.body.removeChild(el);
-
             return (has3d && has3d.length>0 && has3d!=="none");
         })(),
         supersurface, surface, defs, tilegroup, r, g, alength;

js/id/util.js

@@ -70,7 +70,7 @@ iD.util.prefixProperty = function(property) {
         var i = -1, n = p.length, s = document.body.style;
         if (property.toLowerCase() in s) return property.toLowerCase();
         while (++i < n) if (p[i] + property in s) return '-' + p[i].toLowerCase() + '-' + property.toLowerCase();
-        return '';
+        return false;
     })(prefixes);
 };