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
#include "base/files/file_util.h"
#include "base/json/json_writer.h"
#include "components/prefs/pref_service.h"
#include "base/message_loop/message_loop.h"
#include "base/strings/utf_string_conversions.h"
#include "brightray/browser/inspectable_web_contents.h"
#include "brightray/browser/inspectable_web_contents_view.h"
#include "content/browser/renderer_host/render_widget_host_impl.h"
#include "content/public/browser/navigation_entry.h"
#include "content/public/browser/plugin_service.h"
#include "content/public/browser/render_process_host.h"
#include "content/public/browser/render_view_host.h"
#include "content/public/browser/render_widget_host.h"
#include "content/public/browser/render_widget_host_view.h"
#include "content/public/common/content_switches.h"
#include "ipc/ipc_message_macros.h"
#include "native_mate/dictionary.h"
#include "ui/gfx/codec/png_codec.h"
#include "ui/gfx/geometry/point.h"
#include "ui/gfx/geometry/rect.h"
#include "ui/gfx/geometry/size.h"
#include "ui/gfx/geometry/size_conversions.h"
#include "ui/gl/gpu_switching_manager.h"
#if defined(OS_LINUX) || defined(OS_WIN)
#include "content/public/common/renderer_preferences.h"
#include "ui/gfx/font_render_params.h"
#endif
DEFINE_WEB_CONTENTS_USER_DATA_KEY(atom::NativeWindowRelay);
namespace atom {
NativeWindow::NativeWindow(