* 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/api/atom_api_browser_window.h
public content::RenderWidgetHost::InputEventObserver,
                      public content::WebContentsObserver,
                      public ExtendedWebContentsObserver {
 public:
  static mate::WrappableBase* New(mate::Arguments* args);
  static void BuildPrototype(v8::Isolate* isolate,
                             v8::Local<v8::FunctionTemplate> prototype);
  
  static v8::Local<v8::Value> From(v8::Isolate* isolate,
                                   NativeWindow* native_window);
  base::WeakPtr<BrowserWindow> GetWeakPtr() {
    return weak_factory_.GetWeakPtr();
  }
 protected:
  BrowserWindow(v8::Isolate* isolate,
                v8::Local<v8::Object> wrapper,
                const mate::Dictionary& options);
  ~BrowserWindow() override;
  
  void OnInputEvent(const blink::WebInputEvent& event) override;