* Electron version: 1.7.9
* Operating system: macOS 10.13.1

### Expected behavior

If pinch-zoom is disabled via `webFrame.setVisualZoomLevelLimits(1, 1);` it should stay disabled.

### Actual behavior

Pinch zoom is possible. 

### How to reproduce

* connect an external monitor and open any electron app there, keep the macbook pro lid closed
* disconnect the external monitor
* open the lid

=> you can now pinch zoom 
atom/renderer/api/atom_api_web_frame.cc
public:
  explicit FrameSpellChecker(SpellCheckClient* spell_check_client,
                             content::RenderFrame* main_frame)
      : spell_check_client_(spell_check_client), main_frame_(main_frame) {}
  ~FrameSpellChecker() override {
    spell_check_client_ = nullptr;
    main_frame_ = nullptr;
  }
  bool Visit(content::RenderFrame* render_frame) override {
    auto view = render_frame->GetRenderView();
    if (view->GetMainRenderFrame() == main_frame_ ||
        (render_frame->IsMainFrame() && render_frame == main_frame_)) {
      render_frame->GetWebFrame()->SetTextCheckClient(spell_check_client_);
    }
    return true;
  }
 private:
  SpellCheckClient* spell_check_client_;
  content::RenderFrame* main_frame_;
  DISALLOW_COPY_AND_ASSIGN(FrameSpellChecker);
};
}  
WebFrame::WebFrame(v8::Isolate* isolate)