* Electron version: 1.7.6
* Operating system: macOS 10.12, Windows 10

### Expected behavior

Right clicking should open context menu in devtools

### Actual behavior

Right clicking does not open the context menu in devtools

### How to reproduce

- `open Electron.app --args --enable-mixed-sandbox`
- open devtools
- right click in the source tab for example
atom/renderer/atom_sandboxed_renderer_client.cc
mate::Arguments* margs) {
  v8::Local<v8::Object> exports;
  std::string module_key = mate::V8ToString(key);
  mate::Dictionary cache(isolate, GetModuleCache(isolate));
  if (cache.Get(module_key.c_str(), &exports)) {
    return exports;
  }
  auto mod = node::get_builtin_module(module_key.c_str());
  if (!mod) {
    char errmsg[1024];
    snprintf(errmsg, sizeof(errmsg), "No such module: %s", module_key.c_str());
    margs->ThrowError(errmsg);
    return exports;
  }
  exports = v8::Object::New(isolate);
  DCHECK_EQ(mod->nm_register_func, nullptr);
  DCHECK_NE(mod->nm_context_register_func, nullptr);
  mod->nm_context_register_func(exports, v8::Null(isolate),
      isolate->GetCurrentContext(), mod->nm_priv);
  cache.Set(module_key.c_str(), exports);
  return exports;
}
base::CommandLine::StringVector GetArgv() {