The optional Malware Details also collects HTTP cache information. See design...

chrome/browser/safe_browsing/malware_details_cache.cc

Index: chrome/browser/safe_browsing/malware_details_cache.cc
===================================================================
--- chrome/browser/safe_browsing/malware_details_cache.cc	(revision 82879)
+++ chrome/browser/safe_browsing/malware_details_cache.cc	(working copy)
@@ -16,6 +16,7 @@
 #include "chrome/browser/safe_browsing/report.pb.h"
 #include "content/browser/browser_thread.h"
 #include "net/base/load_flags.h"
+#include "net/http/http_response_info.h"
 #include "net/http/http_response_headers.h"
 #include "net/url_request/url_request_context_getter.h"
 #include "net/url_request/url_request_status.h"
@@ -165,6 +166,11 @@
       pb_header->set_value(value);
     }
   }
+
+  net::HostPortPair socket_address = source->socket_address();
+  if (!source->was_fetched_via_proxy()) {
+    pb_response->set_remote_ip(socket_address.ToString());
+  }
 }
 
 void MalwareDetailsCacheCollector::ReadData(