Fix check failure when toggling HTML in show ax tree

Bug: 903588
Change-Id: Ie33670e71e91ec992ea51fc8e1fa2a0416698a91
Reviewed-on: https://chromium-review.googlesource.com/c/1450233
Commit-Queue: Aaron Leventhal <aleventhal@chromium.org>
Commit-Queue: Nektarios Paisios <nektar@chromium.org>
Reviewed-by: Nektarios Paisios <nektar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#628438}

chrome/browser/accessibility/accessibility_ui.cc

@@ -326,6 +326,7 @@ void AccessibilityUIMessageHandler::ToggleAccessibility(
     base::ListValue request_args;
     request_args.Append(std::make_unique<base::Value>(process_id_str));
     request_args.Append(std::make_unique<base::Value>(route_id_str));
+    request_args.Append(std::make_unique<base::Value>("showTree"));
     RequestWebContentsTree(&request_args);
   } else {
     // Call accessibility.showTree without a 'tree' field so the row's