Add a metric to record http response code for download requests.

content/browser/download/download_request_core.cc

Index: content/browser/download/download_request_core.cc
diff --git a/content/browser/download/download_request_core.cc b/content/browser/download/download_request_core.cc
index 7e8d102d55c6b7b99df107aa0e86eb7f542ffa76..21d3deaf8a31b3753ad7b8f5b80379c715e5ecee 100644
--- a/content/browser/download/download_request_core.cc
+++ b/content/browser/download/download_request_core.cc
@@ -251,6 +251,11 @@ bool DownloadRequestCore::OnResponseStarted(
                                            save_info_.get())
           : DOWNLOAD_INTERRUPT_REASON_NONE;
 
+  if (request()->response_headers()) {
+    RecordDownloadHttpResponseCode(
+        request()->response_headers()->response_code());
+  }
+
   std::unique_ptr<DownloadCreateInfo> create_info =
       CreateDownloadCreateInfo(result);
   if (result != DOWNLOAD_INTERRUPT_REASON_NONE) {