We can get the content size and the window size, but not the chrome position.

At the moment we do this:

```
leftBorderWidth = (windowWidth - contentWidth) / 2;
titlebarHeight = windowHeight - (contentHeight + leftBorderWidth);
```

which makes some assumptions so therefore feels a bit wrong.

it would be nice if alongside getContentSize (https://github.com/electron/electron/blob/master/docs/api/browser-window.md#wingetcontentsize) there was a getContentOffset.

I've been looking at the C++ - https://github.com/electron/electron/blob/e05804848f98959d63337aacd9047cd579c5b23f/chromium_src/extensions/browser/app_window/size_constraints.cc and I don't see an easy way to get this information - do you have any ideas or pointers if you accept this as a feature request?

atom/browser/native_window_views.cc
#if defined(OS_WIN)
  HMENU menu = GetSystemMenu(GetAcceleratedWidget(), false);
  if (closable) {
    EnableMenuItem(menu, SC_CLOSE, MF_BYCOMMAND | MF_ENABLED);
  } else {
    EnableMenuItem(menu, SC_CLOSE, MF_BYCOMMAND | MF_DISABLED | MF_GRAYED);
  }
#endif
}
bool NativeWindowViews::IsClosable() {
#if defined(OS_WIN)
  HMENU menu = GetSystemMenu(GetAcceleratedWidget(), false);
  MENUITEMINFO info;
  memset(&info, 0, sizeof(info));
  info.cbSize = sizeof(info);
  info.fMask = MIIM_STATE;
  if (!GetMenuItemInfo(menu, SC_CLOSE, false, &info)) {
    return false;
  }
  return !(info.fState & MFS_DISABLED);
#elif defined(USE_X11)
  return true;
#endif
}
void NativeWindowViews::SetAlwaysOnTop(bool top) {
  window_->SetAlwaysOnTop(top);
}
bool NativeWindowViews::IsAlwaysOnTop() {