use localStorage for user-doc redirect

Chrome doesn't allow cookies for local files, so try
localStorage (and fall back to cookies where localStorage
is unavailable)

original commit: 2312e3b9e6feb4427f582a9a4c6132a8d67cb8f1

pkgs/scribble-pkgs/scribble-lib/scribble/scribble-common.js

@@ -53,7 +53,14 @@ function MergePageArgsIntoLink(a) {
 
 // Cookies --------------------------------------------------------------------
 
+// Actually, try localStorage (a la HTML 5), first.
+
 function GetCookie(key, def) {
+  try {
+    var v = localStorage[key];
+    if (!v) v = def;
+    return v;
+  } catch (e) {
     var i, cookiestrs;
     try {
       if (document.cookie.length <= 0) return def;
@@ -66,15 +73,20 @@ function GetCookie(key, def) {
         return unescape(cur.substring(eql+1));
     }
     return def;
+  }
 }
 
 function SetCookie(key, val) {
+  try {
+    localStorage[key] = val;
+  } catch(e) {
     var d = new Date();
     d.setTime(d.getTime()+(365*24*60*60*1000));
     try {
       document.cookie =
         key + "=" + escape(val) + "; expires="+ d.toGMTString() + "; path=/";
     } catch (e) {}
+  }
 }
 
 // note that this always stores a directory name, ending with a "/"