[NTP Snippets] Add metric for fetch error cases

components/ntp_snippets/ntp_snippets_fetcher.cc

Index: components/ntp_snippets/ntp_snippets_fetcher.cc
diff --git a/components/ntp_snippets/ntp_snippets_fetcher.cc b/components/ntp_snippets/ntp_snippets_fetcher.cc
index 7fe3d94b0e54b22c86e052357ff1bf1e2a1f0f48..3dd50354dd411f89befa333246e436ff2a8b0f39 100644
--- a/components/ntp_snippets/ntp_snippets_fetcher.cc
+++ b/components/ntp_snippets/ntp_snippets_fetcher.cc
@@ -6,6 +6,7 @@
 
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
+#include "base/metrics/sparse_histogram.h"
 #include "base/path_service.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
@@ -120,6 +121,11 @@ void NTPSnippetsFetcher::OnURLFetchComplete(const URLFetcher* source) {
 
   std::string message;
   const URLRequestStatus& status = source->GetStatus();
+
+  UMA_HISTOGRAM_SPARSE_SLOWLY(
+      "NewTabPage.Snippets.FetchHttpResponseOrErrorCode",
+      status.is_success() ? source->GetResponseCode() : status.error());
+
   if (!status.is_success()) {
     message = base::StringPrintf(kStatusMessageURLRequestErrorFormat,
                                  status.error());