Add aria-expanded label to advanced button in interstitials

Bug: 1061611
Change-Id: I3498e5c4c13657d573128c081f1a80097610792d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2583137
Auto-Submit: Carlos IL <carlosil@chromium.org>
Commit-Queue: Emily Stark <estark@chromium.org>
Reviewed-by: Emily Stark <estark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#835552}

components/security_interstitials/core/browser/resources/interstitial_large.js

@@ -59,7 +59,8 @@ function appendDebuggingField(title, value, fixedWidth) {
 }
 
 function toggleDebuggingInfo() {
-  $('error-debugging-info').classList.toggle(HIDDEN_CLASS);
+  const hiddenDebug = $('error-debugging-info').classList.toggle(HIDDEN_CLASS);
+  $('error-code').setAttribute('aria-expanded', !hiddenDebug);
 }
 
 function setupEvents() {
@@ -201,8 +202,12 @@ function setupEvents() {
     // interstitials don't have details buttons.
     $('details-button').classList.add('hidden');
   } else {
+    $('details-button')
+        .setAttribute(
+            'aria-expanded', !$('details').classList.contains(HIDDEN_CLASS));
     $('details-button').addEventListener('click', function(event) {
       const hiddenDetails = $('details').classList.toggle(HIDDEN_CLASS);
+      $('details-button').setAttribute('aria-expanded', !hiddenDetails);
 
       if (mobileNav) {
         // Details appear over the main content on small screens.

components/security_interstitials/core/browser/resources/ssl.js

@@ -21,4 +21,5 @@ function setupSSLDebuggingInfo() {
   }
 
   $('error-code').addEventListener('click', toggleDebuggingInfo);
+  $('error-code').setAttribute('aria-expanded', false);
 }