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.cc
FOR_EACH_OBSERVER(NativeWindowObserver, observers_, OnWindowHide());
}
void NativeWindow::NotifyWindowMaximize() {
  FOR_EACH_OBSERVER(NativeWindowObserver, observers_, OnWindowMaximize());
}
void NativeWindow::NotifyWindowUnmaximize() {
  FOR_EACH_OBSERVER(NativeWindowObserver, observers_, OnWindowUnmaximize());
}
void NativeWindow::NotifyWindowMinimize() {
  FOR_EACH_OBSERVER(NativeWindowObserver, observers_, OnWindowMinimize());
}
void NativeWindow::NotifyWindowRestore() {
  FOR_EACH_OBSERVER(NativeWindowObserver, observers_, OnWindowRestore());
}
void NativeWindow::NotifyWindowResize() {
  FOR_EACH_OBSERVER(NativeWindowObserver, observers_, OnWindowResize());
}
void NativeWindow::NotifyWindowMove() {
  FOR_EACH_OBSERVER(NativeWindowObserver, observers_, OnWindowMove());
}
void NativeWindow::NotifyWindowMoved() {
  FOR_EACH_OBSERVER(NativeWindowObserver, observers_, OnWindowMoved());
}
void NativeWindow::NotifyWindowEnterFullScreen() {
  FOR_EACH_OBSERVER(NativeWindowObserver, observers_,
                    OnWindowEnterFullScreen());
}
void NativeWindow::NotifyWindowScrollTouchBegin() {