[BUGFIX] Fullscreen firefox legacy & chrome

lib/utils/helper.js

@@ -178,17 +178,17 @@ define({
     ctx.fill();
   },
   fullscreen: function fullscreen(btn) {
-    if (!document.fullscreenElement) {
+    if (!document.fullscreenElement && !document.webkitFullscreenElement && !document.mozFullScreenElement) {
       var fel = document.firstElementChild;
       var func = fel.requestFullscreen
         || fel.webkitRequestFullScreen
-        || fel.msRequestFullscreen;
+        || fel.mozRequestFullScreen;
       func.call(fel);
       btn.classList.add('ion-full-exit');
     } else {
       func = document.exitFullscreen
-        || document.webkitexitFullscreen
-        || document.msexitFullscreen;
+        || document.webkitExitFullscreen
+        || document.mozCancelFullScreen;
       if (func) {
         func.call(document);
         btn.classList.add('ion-full-enter');