Fix submenu activation in AppIndicatorIconMenu

menu_model_ refers to the root model, so it was previously checking the
enabled state of the wrong menu model.

Change-Id: Ia1a3662ea68779cbb86663973ba4599d9fabb054
Reviewed-on: https://chromium-review.googlesource.com/c/1336443Reviewed-by: Evan Stade <estade@chromium.org>
Commit-Queue: Jeremy Apthorp <jeremya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608512}

chrome/browser/ui/libgtkui/app_indicator_icon_menu.cc

@@ -116,7 +116,7 @@ void AppIndicatorIconMenu::OnMenuItemActivated(GtkWidget* menu_item) {
     return;
 
   // The menu item can still be activated by hotkeys even if it is disabled.
-  if (menu_model_->IsEnabledAt(id))
+  if (model->IsEnabledAt(id))
     ExecuteCommand(model, id);
 }