* Output of `node_modules/.bin/electron --version`: 2.0.0
* Operating System (Platform and Version): Windows 10

**Expected Behavior**
When I disable a window twice via `setEnabled(false)`, I expect the second disable to have no effect.

**Actual behavior**
The second disable is "queued" up, such that I am forced to enable the window twice to get back to normal.

**To Reproduce**
In the electronquickstart repo, in main.js' `createWindow()`, add these lines:

    mainWindow.setEnabled(false);
    mainWindow.setEnabled(false);
    mainWindow.setEnabled(true);

The window will be disabled when launched. 

You see the same issue if you do it in reverse:

    mainWindow.setEnabled(true);
    mainWindow.setEnabled(false); // this doesn't actually disable it, because the window was enabled from the getgo

If this is expected behavior, can the [docs](https://github.com/electron/electron/blob/master/docs/api/browser-window.md#winsetenabledenable) be updated to explain this behavior.
atom/browser/native_window_views.h
void SetMovable(bool movable) override;
  bool IsMovable() override;
  void SetMinimizable(bool minimizable) override;
  bool IsMinimizable() override;
  void SetMaximizable(bool maximizable) override;
  bool IsMaximizable() override;
  void SetFullScreenable(bool fullscreenable) override;
  bool IsFullScreenable() override;
  void SetClosable(bool closable) override;
  bool IsClosable() override;
  void SetAlwaysOnTop(bool top,
                      const std::string& level,
                      int relativeLevel,
                      std::string* error) override;
  bool IsAlwaysOnTop() override;
  void Center() override;
  void Invalidate() override;
  void SetTitle(const std::string& title) override;
  std::string GetTitle() override;
  void FlashFrame(bool flash) override;
  void SetSkipTaskbar(bool skip) override;
  void SetSimpleFullScreen(bool simple_fullscreen) override;
  bool IsSimpleFullScreen() override;
  void SetKiosk(bool kiosk) override;
  bool IsKiosk() override;
  void SetBackgroundColor(SkColor color) override;
  void SetHasShadow(bool has_shadow) override;
  bool HasShadow() override;
  void SetOpacity(const double opacity) override;
  double GetOpacity() override;