Detect if access to localStorage is forbidden by the user's browser

If the user's cookie/persistent storage setting forbid access to localStorage,
catch the exception and abort the access.

Currently, attempting to use the expand/contract links at the top of the page
for structs/consts/etc. fails due to an unhandled error while accessing
localStorage, if such access is forbidden, as the exception from the failed
access propagates all the way out, interrupting the expand/contract. Instead, I
would like to degrade gracefully; the access won't happen (the collapse/expand
state won't get persisted) but the actual expanding/contracting of the item
will go on to succeed.

Fixes #55079

Author: thanatos

src/librustdoc/html/static/storage.js

@@ -28,6 +28,12 @@ function onEach(arr, func) {
 
 function updateLocalStorage(name, value) {
     if (typeof(Storage) !== "undefined") {
+        try {
+            window.localStorage;
+        } catch(err) {
+            // Storage is supported, but browser preferences deny access to it.
+            return;
+        }
         localStorage[name] = value;
     } else {
         // No Web Storage support so we do nothing