Fix issue where we accessed MenuController after deleting it.

This was introduced in crrev.com/c/1466186 which didn't return right
after the potential call to CancelAll anymore. Instead it would try to
access a member variable and cause a crash.

Bug: 937206
Change-Id: I26a210d464e1c57b071f599e64bcb68a09a16c54
Reviewed-on: https://chromium-review.googlesource.com/c/1496557Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Edin Kadric <edinkadric@google.com>
Cr-Commit-Position: refs/heads/master@{#636964}

ui/views/controls/menu/menu_controller.cc

@@ -1183,8 +1183,11 @@ ui::PostDispatchAction MenuController::OnWillDispatchKeyEvent(
   ViewsDelegate::ProcessMenuAcceleratorResult result =
       ViewsDelegate::GetInstance()->ProcessAcceleratorWhileMenuShowing(
           accelerator);
-  if (result == ViewsDelegate::ProcessMenuAcceleratorResult::CLOSE_MENU)
+  if (result == ViewsDelegate::ProcessMenuAcceleratorResult::CLOSE_MENU) {
     CancelAll();
+    event->StopPropagation();
+    return ui::POST_DISPATCH_NONE;
+  }
 
   if (IsEditableCombobox()) {
     const base::flat_set<ui::KeyboardCode> kKeysThatDontPropagate = {