Client, polyfills: check for sessionStorage using a more cross-browse…

…r (apparently) way

client/galaxy/scripts/mvc/base-mvc.js

@@ -66,7 +66,7 @@ var SessionStorageModel = Backbone.Model.extend({
 
     _checkEnabledSessionStorage : function(){
         try {
-            return sessionStorage.length;
+            return window.sessionStorage.length >= 0;
         } catch( err ){
             alert( 'Please enable cookies in your browser for this Galaxy site' );
             return false;

client/galaxy/scripts/polyfills.js

@@ -51,25 +51,25 @@
     };
 
     // ------------------------------------------------------------------ can't/won't polyfill
-    var incompatibilities = [
+    var features = [
         { name: 'canvas',           compatible: function(){ return window.CanvasRenderingContext2D; } },
         { name: 'sessionStorage',   compatible: function(){
             try {
-                return Number.isInteger( sessionStorage.length );
+                return window.sessionStorage.length >= 0;
             } catch( err ){}
             return false;
         }},
     ];
     // build a list of feature names for features that were not found
-    incompatibilities = incompatibilities
+    var incompatibilities = features
         .filter( function( feature ){ return !feature.compatible(); })
         .map( function( feature ){ return feature.name; });
 
     // if there are needed features missing, follow the index link to the static incompat warning
     if( !!incompatibilities.length ){
         var root = document.querySelectorAll( 'link[rel="index"]' ).item( 0 );
         if( root ){
-            window.location.href = root.href + 'static/incompatible-browser.html';
+            window.location = root.href + 'static/incompatible-browser.html';
         }
         console.log( 'incompatible browser:\n' + incompatibilities.join( '\n' ) );
     }