* Electron Version: 3.0.0-beta1
* Operating System (Platform and Version): macOS
* Last known working Electron version: 2.0.2

**Expected Behavior**
```css
html, body, * {
    -webkit-app-region: drag;
    -webkit-user-select: none;
    cursor: default;
}
```
should allow users to move the position of the window by dragging it directly.

**Actual behavior**
The window is not draggable.
The `cursor` and `-webkit-user-select` properties work well.

**To Reproduce**
copy the CSS above, paste it into a frameless app's `<style>` tag, and run the app.

**Screenshots**

**Additional Information**

atom/browser/native_window_mac.h
#ifndef ATOM_BROWSER_NATIVE_WINDOW_MAC_H_
#define ATOM_BROWSER_NATIVE_WINDOW_MAC_H_
#import <Cocoa/Cocoa.h>
#include <string>
#include <vector>
#include "atom/browser/native_window.h"
#include "base/mac/scoped_nsobject.h"
#include "ui/views/controls/native/native_view_host.h"
@class AtomNSWindow;
@class AtomNSWindowDelegate;
@class AtomPreviewItem;
@class AtomTouchBar;
@class CustomWindowButtonView;
@class FullSizeContentView;
namespace atom {
class RootViewMac;
class NativeWindowMac : public NativeWindow {
 public:
  NativeWindowMac(const mate::Dictionary& options, NativeWindow* parent);
  ~NativeWindowMac() override;
  
  void SetContentView(views::View* view) override;
  void Close() override;
  void CloseImmediately() override;
  void Focus(bool focus) override;
  bool IsFocused() override;