* Electron version: v1.4.5
* Operating system: Windows 10

### Expected behavior

If disabled menu items have accelerators, they can be triggered using that accelerator. Since disabled menu items are not clickable, one would expect that they can't be triggered in any way.

### Actual behavior

You can trigger disabled menu items with accelerators by pressing the corresponding accelerator.

### How to reproduce

In the default app, just set the `enabled` property on the 'Toggle Developer Tools' menu item to `false`. Observe that by pressing 'Ctrl+Shift+I' we can still trigger the menu item.

atom/browser/ui/accelerator_util.cc
atom::AtomMenuModel* model) {
  int count = model->GetItemCount();
  for (int i = 0; i < count; ++i) {
    atom::AtomMenuModel::ItemType type = model->GetTypeAt(i);
    if (type == atom::AtomMenuModel::TYPE_SUBMENU) {
      auto submodel = model->GetSubmenuModelAt(i);
      GenerateAcceleratorTable(table, submodel);
    } else {
      ui::Accelerator accelerator;
      if (model->GetAcceleratorAtWithParams(i, true, &accelerator)) {
        MenuItem item = { i, model };
        (*table)[accelerator] = item;
      }
    }
  }
}
bool TriggerAcceleratorTableCommand(AcceleratorTable* table,
                                    const ui::Accelerator& accelerator) {
  if (ContainsKey(*table, accelerator)) {
    const accelerator_util::MenuItem& item = (*table)[accelerator];
    item.model->ActivatedAt(item.position);
    return true;
  } else {
    return false;
  }
}
}