* 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.cc
#if defined(OS_MACOSX)
  if (!draggable_regions_.empty())
    UpdateDraggableRegions(nullptr, draggable_regions_);
#endif
  TopLevelWindow::OnWindowResize();
}
void BrowserWindow::OnWindowLeaveFullScreen() {
  TopLevelWindow::OnWindowLeaveFullScreen();
#if defined(OS_MACOSX)
  if (web_contents()->IsFullscreenForCurrentTab())
    web_contents()->ExitFullscreen(true);
#endif
}
void BrowserWindow::Focus() {
  if (api_web_contents_->IsOffScreen())
    FocusOnWebView();
  else
    TopLevelWindow::Focus();
}
void BrowserWindow::Blur() {
  if (api_web_contents_->IsOffScreen())
    BlurWebView();
  else
    TopLevelWindow::Blur();
}
void BrowserWindow::SetBackgroundColor(const std::string& color_name) {