* 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
void SetIgnoreMouseEvents(bool ignore, bool forward) override;
  void SetContentProtection(bool enable) override;
  void SetBrowserView(NativeBrowserView* browser_view) override;
  void SetParentWindow(NativeWindow* parent) override;
  gfx::NativeView GetNativeView() const override;
  gfx::NativeWindow GetNativeWindow() const override;
  gfx::AcceleratedWidget GetAcceleratedWidget() const override;
  void SetProgressBar(double progress, const ProgressState state) override;
  void SetOverlayIcon(const gfx::Image& overlay,
                      const std::string& description) override;
  void SetVisibleOnAllWorkspaces(bool visible) override;
  bool IsVisibleOnAllWorkspaces() override;
  void SetAutoHideCursor(bool auto_hide) override;
  void SelectPreviousTab() override;
  void SelectNextTab() override;
  void MergeAllWindows() override;
  void MoveTabToNewWindow() override;
  void ToggleTabBar() override;
  bool AddTabbedWindow(NativeWindow* window) override;
  void SetVibrancy(const std::string& type) override;
  void SetTouchBar(
      const std::vector<mate::PersistentDictionary>& items) override;
  void RefreshTouchBarItem(const std::string& item_id) override;
  void SetEscapeTouchBarItem(const mate::PersistentDictionary& item) override;
  gfx::Rect ContentBoundsToWindowBounds(const gfx::Rect& bounds) const override;
  gfx::Rect WindowBoundsToContentBounds(const gfx::Rect& bounds) const override;
  
  void SetStyleMask(bool on, NSUInteger flag);
  void SetCollectionBehavior(bool on, NSUInteger flag);
  enum TitleBarStyle {