* 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
#include "atom/browser/api/atom_api_browser_window.h"
#include "atom/browser/browser.h"
#include "atom/browser/unresponsive_suppressor.h"
#include "atom/browser/web_contents_preferences.h"
#include "atom/browser/window_list.h"
#include "atom/common/api/api_messages.h"
#include "atom/common/api/constructor.h"
#include "atom/common/color_util.h"
#include "atom/common/native_mate_converters/callback.h"
#include "atom/common/native_mate_converters/value_converter.h"
#include "atom/common/options_switches.h"
#include "base/threading/thread_task_runner_handle.h"
#include "content/browser/renderer_host/render_widget_host_impl.h"
#include "content/public/browser/render_process_host.h"
#include "content/public/browser/render_view_host.h"
#include "native_mate/dictionary.h"
#include "ui/gl/gpu_switching_manager.h"
#include "atom/common/node_includes.h"
namespace atom {
namespace api {
BrowserWindow::BrowserWindow(v8::Isolate* isolate,
                             v8::Local<v8::Object> wrapper,
                             const mate::Dictionary& options)
    : TopLevelWindow(isolate, options), weak_factory_(this) {
  mate::Handle<class WebContents> web_contents;