Record request initiator on DumpWithoutCrash

This CL records a network::ResourceRequest::request_initiator in
addition to some pre-existing members, upon referrer mismatch
DumpWithoutCrash. It will help in debugging crbug.com/1021908.

R=yhirano@chromium.org

Bug: 1021908
Change-Id: I91e6b1634449658ce42421b83b72ce3bc23783d1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1908711Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Dominic Farolino <dom@chromium.org>
Cr-Commit-Position: refs/heads/master@{#715195}

services/network/public/cpp/url_request_mojom_traits.h

@@ -110,6 +110,9 @@ struct COMPONENT_EXPORT(NETWORK_CPP_BASE)
         base::debug::Alias(&referrer_policy);
         DEBUG_ALIAS_FOR_GURL(target_buf, request.url);
         DEBUG_ALIAS_FOR_GURL(referrer_buf, request.referrer);
+        DEBUG_ALIAS_FOR_GURL(
+            initiator_buf,
+            request.request_initiator.value_or(url::Origin()).GetURL())
         base::debug::DumpWithoutCrashing();
       }
     }