Simplify getViewportSize function to use the jQuery height and width …

…functions

Signed-off-by: Tim Almdal <tnalmdal@shaw.ca>

lib/gallery.common.js

@@ -33,14 +33,10 @@
   $.getViewportSize = function() {
     return {
       width : function() {
-        return window.innerWidth
-          || document.documentElement && document.documentElement.clientWidth
-          || document.body.clientWidth;
+        return $(window).width();
       },
       height : function() {
-        return window.innerHeight
-          || document.documentElement && document.documentElement.clientHeight
-          || document.body.clientHeight;
+        return $(window).height();
       }
     };
   };