* 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
blink::WebFrame* frame = web_frame_->Parent();
  if (frame && frame->IsWebLocalFrame())
    return mate::CreateHandle(isolate(),
                              new WebFrame(isolate(),
                                           frame->ToWebLocalFrame())).ToV8();
  else
    return v8::Null(isolate());
}
v8::Local<v8::Value> WebFrame::Top() const {
  blink::WebFrame* frame = web_frame_->Top();
  if (frame && frame->IsWebLocalFrame())
    return mate::CreateHandle(isolate(),
                              new WebFrame(isolate(),
                                           frame->ToWebLocalFrame())).ToV8();
  else
    return v8::Null(isolate());
}
v8::Local<v8::Value> WebFrame::FirstChild() const {
  blink::WebFrame* frame = web_frame_->FirstChild();
  if (frame && frame->IsWebLocalFrame())
    return mate::CreateHandle(isolate(),
                              new WebFrame(isolate(),
                                           frame->ToWebLocalFrame())).ToV8();
  else
    return v8::Null(isolate());
}
v8::Local<v8::Value> WebFrame::NextSibling() const {