Fix Menu.append act different from SimpleMenuModel cause crash

[waivital]

NWJS Version : nwjs-v0.45.0-beta1-linux-x64.tar.gz
Operating System : Ubuntu 19.10

Expected behavior

Popup menu become empty

Actual behavior

Program crashed

How to reproduce

Use the script below, then right click the body, select Trigger Remove All MenuItem

<script>
var menu = new nw.Menu();

menu.append(new nw.MenuItem({ type: 'separator' }));
menu.append(new nw.MenuItem({
  label: 'Trigger Remove All MenuItem',
  click: function(){
    var i = menu.items.length - 1
    while (i >= 0) {
      menu.removeAt(i)
      i--
    }
  }
}));
menu.append(new nw.MenuItem({ label: 'Item B' }));
menu.append(new nw.MenuItem({ type: 'separator' }));
menu.append(new nw.MenuItem({ type: 'separator' }))
menu.append(new nw.MenuItem({ label: 'Item C' }));

document.body.addEventListener('contextmenu', function(ev) {
  ev.preventDefault();
  menu.popup(ev.x, ev.y);
  return false;
}, false);
</script>

The output

[8784:8784:0327/063840.807725:ERROR:component_loader.cc(169)] Failed to parse extension manifest.
[8784:8784:0327/063840.836020:ERROR:browser_switcher_service.cc(238)] XXX Init()
[8784:8784:0327/063842.557524:FATAL:simple_menu_model.cc(539)] Check failed: static_cast<size_t>(index) < items_.size() (5 vs. 4)
#0 0x7f3ae7c65629 (/nwjs/lib/libnw.so+0x4694628)
Task trace:
#0 0x7f3ae85d07f6 (/nwjs/lib/libnw.so+0x4fff7f5)
#1 0x7f3ae7daf9d6 (/nwjs/lib/libnw.so+0x47de9d5)
IPC message handler context: 0x73E4B09C

[1]    8784 abort (core dumped)  ./nwjs/nw .

[waivital]

During the test, I found a bug will cause unused MenuItem not collected by the gc. I put its fix also in this pr for convenient :D .

Here is the reproducing code

function tryLeak() {
  console.log('Processing...')
  var i = 10000
  while (i > 0) {
    const item = new nw.MenuItem({ label: 'My-b10e17ab-44c9-MenuItem' })
    menu.append(item)
    menu.remove(item)
    i--
  }
  console.log('Done!')
}

The heap snapshot

before run

after run

[waivital]

@rogerwang can you have a look at the PR? If there's something more required, let me know.

[rogerwang]

Thanks. Will see it soon.

[pragma-git]

I also have this problem at v0.50.1. I have a nagging feeling this is causing some problem on WIndows for my app, whereas MacOS works fine (but Heap MenuItems are not gc:ed here either)