* 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
: web_frame_(blink::WebLocalFrame::FrameForCurrentContext()) {
  Init(isolate);
}
WebFrame::WebFrame(v8::Isolate* isolate, blink::WebLocalFrame* blink_frame)
    : web_frame_(blink_frame) {
  Init(isolate);
}
WebFrame::~WebFrame() {
}
void WebFrame::SetName(const std::string& name) {
  web_frame_->SetName(blink::WebString::FromUTF8(name));
}
double WebFrame::SetZoomLevel(double level) {
  double result = 0.0;
  content::RenderFrame* render_frame =
      content::RenderFrame::FromWebFrame(web_frame_);
  render_frame->Send(new AtomFrameHostMsg_SetTemporaryZoomLevel(
      render_frame->GetRoutingID(), level, &result));
  return result;
}
double WebFrame::GetZoomLevel() const {
  double result = 0.0;
  content::RenderFrame* render_frame =
      content::RenderFrame::FromWebFrame(web_frame_);
  render_frame->Send(
      new AtomFrameHostMsg_GetZoomLevel(render_frame->GetRoutingID(), &result));
  return result;
}
double WebFrame::SetZoomFactor(double factor) {