* 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
content::RenderFrame::FromWebFrame(web_frame_)->AttachGuest(id);
}
void WebFrame::DetachGuest(int id) {
  content::RenderFrame::FromWebFrame(web_frame_)->DetachGuest(id);
}
void WebFrame::SetSpellCheckProvider(mate::Arguments* args,
                                     const std::string& language,
                                     bool auto_spell_correct_turned_on,
                                     v8::Local<v8::Object> provider) {
  if (!provider->Has(mate::StringToV8(args->isolate(), "spellCheck"))) {
    args->ThrowError("\"spellCheck\" has to be defined");
    return;
  }
  std::unique_ptr<SpellCheckClient> client(new SpellCheckClient(
      language, auto_spell_correct_turned_on, args->isolate(), provider));
  
  
  FrameSpellChecker spell_checker(
      client.get(), content::RenderFrame::FromWebFrame(web_frame_));
  content::RenderFrame::ForEach(&spell_checker);
  spell_check_client_.swap(client);
  web_frame_->SetSpellCheckPanelHostClient(spell_check_client_.get());
}
void WebFrame::RegisterURLSchemeAsSecure(const std::string& scheme) {
  
  blink::SchemeRegistry::RegisterURLSchemeAsSecure(
      WTF::String::FromUTF8(scheme.data(), scheme.length()));
}
void WebFrame::RegisterURLSchemeAsBypassingCSP(const std::string& scheme) {