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* Electron version: 1.7.2
* Operating system: macOS Sierra

### Expected behavior

Webview appear

### Actual behavior

It don't

### How to reproduce

1. Create a browser window with contextIsolation on true and webviewTag on true
2. Inside of it, add a webview
3. Run it, webview should not appear

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atom/renderer/atom_render_frame_observer.cc
v8::Local<v8::Context> context,
                  bool internal,
                  v8::Local<v8::Object>* ipc) {
  v8::Local<v8::String> key =
      mate::StringToV8(isolate, internal ? "ipc-internal" : "ipc");
  v8::Local<v8::Private> privateKey = v8::Private::ForApi(isolate, key);
  v8::Local<v8::Object> global_object = context->Global();
  v8::Local<v8::Value> value;
  if (!global_object->GetPrivate(context, privateKey).ToLocal(&value))
    return false;
  if (value.IsEmpty() || !value->IsObject())
    return false;
  *ipc = value->ToObject(isolate);
  return true;
}
std::vector<v8::Local<v8::Value>> ListValueToVector(