[chrome:accessibility] Only allow event recording on one page at a time.

Prevent a user from clicking Start recording on multiple pages at the same
time by disabling all Start recording buttons when one has been pressed.
This prevents a crash which would occur when a user would click
Start recording on multiple pages without stopping the recording.

Bug: 1036755, 785493
Change-Id: I58cdd9be1595dac679f4bfa488599bc198863c18
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1997946
Commit-Queue: Abigail Klein <abigailbklein@google.com>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#731782}

chrome/browser/accessibility/accessibility_ui.cc

@@ -660,6 +660,9 @@ void AccessibilityUIMessageHandler::RequestAccessibilityEvents(
   content::WebContents* web_contents =
       content::WebContents::FromRenderViewHost(rvh);
   if (start) {
+    if (observer_) {
+      return;
+    }
     web_contents->RecordAccessibilityEvents(
         base::BindRepeating(&AccessibilityUIMessageHandler::Callback,
                             base::Unretained(this)),

chrome/browser/resources/accessibility/accessibility.js

@@ -106,13 +106,25 @@ cr.define('accessibility', function() {
       element.textContent = 'Stop recording';
       element.setAttribute('aria-expanded', 'true');
 
-      // TODO Hide all other start recording elements. UI should reflect the
-      // fact that there can only be one accessibility recorder at once.
+      // Disable all other start recording buttons. UI reflects the fact that
+      // there can only be one accessibility recorder at once.
+      const buttons = document.getElementsByClassName('recordEventsButton');
+      for (const button of buttons) {
+        if (button != element) {
+          button.disabled = true;
+        }
+      }
     } else {
       element.textContent = 'Start recording';
       element.setAttribute('aria-expanded', 'false');
 
-      // TODO Show all start recording elements.
+      // Enable all start recording buttons.
+      const buttons = document.getElementsByClassName('recordEventsButton');
+      for (const button of buttons) {
+        if (button != element) {
+          button.disabled = false;
+        }
+      }
     }
     chrome.send('requestAccessibilityEvents', [
       {'processId': data.processId, 'routingId': data.routingId, 'start': start}
@@ -368,6 +380,7 @@ cr.define('accessibility', function() {
 
   function createStartStopAccessibilityEventRecordingElement(data, id) {
     const show = document.createElement('button');
+    show.classList.add('recordEventsButton');
     show.textContent = 'Start recording';
     show.id = id + ':startOrStopEvents';
     show.setAttribute('aria-expanded', 'false');