* 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
TopLevelWindow::SetBackgroundColor(color_name);
  auto* view = web_contents()->GetRenderWidgetHostView();
  if (view)
    view->SetBackgroundColor(ParseHexColor(color_name));
}
void BrowserWindow::SetBrowserView(v8::Local<v8::Value> value) {
  TopLevelWindow::SetBrowserView(value);
#if defined(OS_MACOSX)
  UpdateDraggableRegions(nullptr, draggable_regions_);
#endif
}
void BrowserWindow::SetVibrancy(mate::Arguments* args) {
  std::string type;
  args->GetNext(&type);
  auto* render_view_host = web_contents()->GetRenderViewHost();
  if (render_view_host) {
    auto* impl = content::RenderWidgetHostImpl::FromID(
        render_view_host->GetProcess()->GetID(),
        render_view_host->GetRoutingID());
    if (impl)
      impl->SetBackgroundOpaque(type.empty() ? !window_->transparent() : false);
  }
  TopLevelWindow::SetVibrancy(args);
}
void BrowserWindow::FocusOnWebView() {