[WebID] Make requests for well-known json file credentialed

For the purposes of testing on WebID-supporting IdP services running on
private infrastructure, this adds cookies to the requests to
/.well-known/webid.

Bug: 1159177
Change-Id: I507c461bc8d87d91f8d8d8d25565e1402b053999
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2593696Reviewed-by: Sam Goto <goto@chromium.org>
Commit-Queue: Ken Buchanan <kenrb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#837757}

content/browser/webid/idp_network_request_manager.cc

@@ -115,7 +115,13 @@ void IdpNetworkRequestManager::FetchIDPWellKnown(
 
   auto resource_request = std::make_unique<network::ResourceRequest>();
   resource_request->url = target_url;
-  resource_request->credentials_mode = network::mojom::CredentialsMode::kOmit;
+  // TODO(kenrb): credentials_mode should be kOmit, but for prototyping
+  // purposes it is useful to be able to run test IdPs on services that always
+  // require cookies. This needs to be changed back when a better solution is
+  // found or those test IdPs are no longer required.
+  // See https://crbug.com/1159177.
+  resource_request->credentials_mode =
+      network::mojom::CredentialsMode::kInclude;
   resource_request->headers.SetHeader(net::HttpRequestHeaders::kAccept,
                                       kAcceptMimeType);
   resource_request->request_initiator =