Segfault in `base::SequenceCheckerImpl::CalledOnValidSequence()`.

Seen [in this CI run](https://app.circleci.com/pipelines/github/electron/electron/32652/workflows/d9f0c307-7021-453d-8bec-6b2eb9bd2bc2/jobs/718582). 

```
Received signal 11 <unknown> 000000000000
0   Electron Framework                  0x000000011ab9ece9 base::debug::CollectStackTrace(void**, unsigned long) + 9
1   Electron Framework                  0x000000011aa931e3 base::debug::StackTrace::StackTrace() + 19
2   Electron Framework                  0x000000011ab9ebb1 base::debug::(anonymous namespace)::StackDumpSignalHandler(int, __siginfo*, void*) + 2385
3   libsystem_platform.dylib            0x00007fff68b8c5fd _sigtramp + 29
4   ???                                 0x0000000000000000 0x0 + 0
5   Electron Framework                  0x000000011ab09bda base::SequenceCheckerImpl::CalledOnValidSequence() const + 42
6   Electron Framework                  0x000000011ab25bd9 base::SupportsUserData::GetUserData(void const*) const + 25
7   Electron Framework                  0x000000011526f1d2 electron::api::WebContents::DidStopLoading() + 50
8   Electron Framework                  0x0000000119bc2401 content::WebContentsImpl::LoadingStateChanged(bool, content::LoadNotificationDetails*) + 2049
9   Electron Framework                  0x0000000119bcab12 content::WebContentsImpl::DidStopLoading() + 178
10  Electron Framework                  0x000000011983fcc8 content::FrameTreeNode::DidStopLoading() + 120
11  Electron Framework                  0x0000000119937cd5 content::RenderFrameHostImpl::DidStopLoading() + 133
12  Electron Framework                  0x0000000116b3d1fa content::mojom::FrameHostStubDispatch::Accept(content::mojom::FrameHost*, mojo::Message*) + 3610
13  Electron Framework                  0x000000011b058953 mojo::InterfaceEndpointClient::HandleValidatedMessage(mojo::Message*) + 931
14  Electron Framework                  0x000000011b05c62f mojo::MessageDispatcher::Accept(mojo::Message*) + 191
15  Electron Framework                  0x000000011b059e71 mojo::InterfaceEndpointClient::HandleIncomingMessage(mojo::Message*) + 97
16  Electron Framework                  0x000000011b0b8132 IPC::(anonymous namespace)::ChannelAssociatedGroupController::AcceptOnProxyThread(mojo::Message) + 706
17  Electron Framework                  0x000000011b0b4f8c base::internal::Invoker<base::internal::BindState<void (IPC::(anonymous namespace)::ChannelAssociatedGroupController::*)(mojo::Message), scoped_refptr<IPC::(anonymous namespace)::ChannelAssociatedGroupController>, mojo::Message>, void ()>::RunOnce(base::internal::BindStateBase*) + 140
18  Electron Framework                  0x000000011ab2e20b base::TaskAnnotator::RunTask(char const*, base::PendingTask*) + 395
19  Electron Framework                  0x000000011ab4d1b0 base::sequence_manager::internal::ThreadControllerWithMessagePumpImpl::DoWorkImpl(base::sequence_manager::LazyNow*) + 528
20  Electron Framework                  0x000000011ab4ce08 base::sequence_manager::internal::ThreadControllerWithMessagePumpImpl::DoWork() + 168
21  Electron Framework                  0x000000011abbede1 base::MessagePumpCFRunLoopBase::RunWork() + 65
22  Electron Framework                  0x000000011abb4162 base::mac::CallWithEHFrame(void () block_pointer) + 10
23  Electron Framework                  0x000000011abbe7af base::MessagePumpCFRunLoopBase::RunWorkSource(v
```
shell/browser/api/electron_api_web_contents.cc
GURL http_referrer;
    if (options.Get("httpReferrer", &http_referrer))
      params.referrer =
          content::Referrer(http_referrer.GetAsReferrer(),
                            network::mojom::ReferrerPolicy::kDefault);
  }
  std::string user_agent;
  if (options.Get("userAgent", &user_agent))
    ontents()->SetUserAgentOverride(
        blink::UserAgentOverride::UserAgentOnly(user_agent), false);
  std::string extra_headers;
  if (options.Get("extraHeaders", &extra_headers))
    params.extra_headers = extra_headers;
  scoped_refptr<network::ResourceRequestBody> body;
  if (options.Get("postData", &body)) {
    params.post_data = body;
    params.load_type = content::NavigationController::LOAD_TYPE_HTTP_POST;
  }
  GURL base_url_for_data_url;
  if (options.Get("baseURLForDataURL", &base_url_for_data_url)) {
    params.base_url_for_data_url = base_url_for_data_url;
    params.load_type = content::NavigationController::LOAD_TYPE_DATA;
  }
  bool reload_ignoring_cache = false;
  if (options.Get("reloadIgnoringCache", &reload_ignoring_cache) &&
      reload_ignoring_cache) {
    params.reload_type = content::ReloadType::BYPASSING_CACHE;
  }
   Calling LoadURLWithParams() can trigger JS which destroys |this|.
  auto weak_this = GetWeakPtr();