Repro steps:
1. Start with a fresh/clean profile and --site-per-process:
   $ out/rel/chrome --user-data-dir=$HOME/.chrome-kill-unique-number-here --site-per-process
2. Click the user/avator icon in the top-right corner
3. Click "Sign in to Chromium"
4. Sign-in
5. Observe the following crash:

[76021:76032:0410/085007.745554:FATAL:web_request_permissions.cc(109)] Check failed: IsWebUIAllowedToMakeNetworkRequests(*initiator). Unsupported network request from chrome://sync-confirmation/ for https://lh3.googleusercontent.com/-XdUIqdMkCWA/AAAAAAAAAAI/AAAAAAAAAAA/4252rscbv5M/s128-c/photo.jpg
#0 0x7fc7e35de40c base::debug::StackTrace::StackTrace()
#1 0x7fc7e36088bb logging::LogMessage::~LogMessage()
#2 0x565094b247d7 IsSensitiveURL()
#3 0x565094b24bc3 WebRequestPermissions::HideRequest()
#4 0x565094b0f176 extensions::ExtensionWebRequestEventRouter::OnBeforeRequest()
#5 0x565094e3410c ChromeNetworkDelegate::OnBeforeURLRequest()
#6 0x7fc7e226b0d1 net::NetworkDelegate::NotifyBeforeURLRequest()
#7 0x7fc7e226b0d1 net::NetworkDelegate::NotifyBeforeURLRequest()
#8 0x7fc7e226b0d1 net::NetworkDelegate::NotifyBeforeURLRequest()
#9 0x7fc7e258e140 net::URLRequest::Start()
#10 0x7fc7e0d5025c content::ResourceLoader::StartRequestInternal()
#11 0x7fc7e0d4fafd content::ResourceLoader::Resume()
#12 0x7fc7e0d4c4e0 content::ResourceLoader::StartRequest()
#13 0x7fc7e0d47ca7 content::ResourceDispatcherHostImpl::StartLoading()
#14 0x7fc7e0d4430f content::ResourceDispatcherHostImpl::BeginRequestInternal()
#15 0x7fc7e0d4389f content::ResourceDispatcherHostImpl::ContinuePendingBeginRequest()
#16 0x7fc7e0d4096c content::ResourceDispatcherHostImpl::BeginRequest()
#17 0x7fc7e0d401e2 content::ResourceDispatcherHostImpl::OnRequestResourceInternal()
#18 0x7fc7e0d47824 content::ResourceDispatcherHostImpl::OnRequestResourceWithMojo()
#19 0x7fc7e0d58aaf content::URLLoaderFactoryImpl::CreateLoaderAndStart()
#20 0x7fc7e0d5245e content::ResourceMessageFilter::CreateLoaderAndStart()
#21 0x7fc7e0635643 network::mojom::URLLoaderFactoryStubDispatch::Accept()