Add CHECK to help investigate crash.

Bug: 461981
Change-Id: I2e58d90f9f9e2a983286fbec9742234838fbbf50
Reviewed-on: https://chromium-review.googlesource.com/c/1335951
Commit-Queue: Zhongyi Shi <zhongyi@chromium.org>
Reviewed-by: Zhongyi Shi <zhongyi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608236}

net/http/http_stream_factory_job_controller.cc

@@ -259,6 +259,10 @@ void HttpStreamFactory::JobController::OnStreamReady(
   DCHECK(!is_websocket_);
   DCHECK_EQ(HttpStreamRequest::HTTP_STREAM, request_->stream_type());
   OnJobSucceeded(job);
+
+  // TODO(bnc): Remove when https://crbug.com/461981 is fixed.
+  CHECK(request_);
+
   DCHECK(request_->completed());
   delegate_->OnStreamReady(used_ssl_config, job->proxy_info(),
                            std::move(stream));