[remote suggestions] Attach the fetch time to RemoteSnippets, ContentSnippets and SnippetArticle

components/ntp_snippets/remote/remote_suggestions_fetcher.cc

Index: components/ntp_snippets/remote/remote_suggestions_fetcher.cc
diff --git a/components/ntp_snippets/remote/remote_suggestions_fetcher.cc b/components/ntp_snippets/remote/remote_suggestions_fetcher.cc
index 3722a2faa8ca7a0974ea70c28e3c0b3aaa91a902..aaf62363636a124ce811644b82fd0df14c2bd6d5 100644
--- a/components/ntp_snippets/remote/remote_suggestions_fetcher.cc
+++ b/components/ntp_snippets/remote/remote_suggestions_fetcher.cc
@@ -136,7 +136,8 @@ bool UsesChromeContentSuggestionsAPI(const GURL& endpoint) {
 bool AddSuggestionsFromListValue(bool content_suggestions_api,
                                  int remote_category_id,
                                  const base::ListValue& list,
-                                 RemoteSuggestion::PtrVector* suggestions) {
+                                 RemoteSuggestion::PtrVector* suggestions,
+                                 const base::Time& fetch_time) {
   for (const auto& value : list) {
     const base::DictionaryValue* dict = nullptr;
     if (!value->GetAsDictionary(&dict)) {
@@ -146,9 +147,10 @@ bool AddSuggestionsFromListValue(bool content_suggestions_api,
     std::unique_ptr<RemoteSuggestion> suggestion;
     if (content_suggestions_api) {
       suggestion = RemoteSuggestion::CreateFromContentSuggestionsDictionary(
-          *dict, remote_category_id);
+          *dict, remote_category_id, fetch_time);
     } else {
-      suggestion = RemoteSuggestion::CreateFromChromeReaderDictionary(*dict);
+      suggestion =
+          RemoteSuggestion::CreateFromChromeReaderDictionary(*dict, fetch_time);
     }
     if (!suggestion) {
       return false;
@@ -442,6 +444,10 @@ void RemoteSuggestionsFetcher::JsonRequestDone(
     FetchResult status_code,
     const std::string& error_details) {
   DCHECK(request);
+  // Record the time when request for fetching remote content snippets finished.
+  const base::Time fetch_time = base::Time::FromInternalValue(
+      tick_clock_->NowTicks().ToInternalValue());

[Marc Treib, 2017/02/13 10:24:49]

Hrm, this is a bit ugly, and I'm not entirely convinced it's safe...
I guess the "proper" way would be to also inject a (non-Tick) Clock and use that
here, but I'm not sure it's worth the effort.
WDYT?

[markusheintz_, 2017/02/13 11:19:16]

I share your concerns and I fully agree. I'm actually already working at it. I
was only side tracked by reviewing another CL.

+
   last_fetch_json_ = request->GetResponseString();
 
   UMA_HISTOGRAM_TIMES("NewTabPage.Snippets.FetchTime",
@@ -453,7 +459,8 @@ void RemoteSuggestionsFetcher::JsonRequestDone(
     return;
   }
   FetchedCategoriesVector categories;
-  if (!JsonToSnippets(*result, &categories)) {
+
+  if (!JsonToSnippets(*result, &categories, fetch_time)) {
     LOG(WARNING) << "Received invalid snippets: " << last_fetch_json_;
     FetchFinished(OptionalFetchedCategories(), std::move(callback),
                   FetchResult::INVALID_SNIPPET_CONTENT_ERROR, std::string());
@@ -489,7 +496,8 @@ void RemoteSuggestionsFetcher::FetchFinished(
 
 bool RemoteSuggestionsFetcher::JsonToSnippets(
     const base::Value& parsed,
-    FetchedCategoriesVector* categories) {
+    FetchedCategoriesVector* categories,
+    const base::Time& fetch_time) {
   const base::DictionaryValue* top_dict = nullptr;
   if (!parsed.GetAsDictionary(&top_dict)) {
     return false;
@@ -504,9 +512,9 @@ bool RemoteSuggestionsFetcher::JsonToSnippets(
 
       const base::ListValue* recos = nullptr;
       return top_dict->GetList("recos", &recos) &&
-             AddSuggestionsFromListValue(/*content_suggestions_api=*/false,
-                                         kUnusedRemoteCategoryId, *recos,
-                                         &categories->back().suggestions);
+             AddSuggestionsFromListValue(
+                 /*content_suggestions_api=*/false, kUnusedRemoteCategoryId,
+                 *recos, &categories->back().suggestions, fetch_time);
     }
 
     case FetchAPI::CHROME_CONTENT_SUGGESTIONS_API: {
@@ -533,7 +541,7 @@ bool RemoteSuggestionsFetcher::JsonToSnippets(
         if (category_value->GetList("suggestions", &suggestions_list)) {
           if (!AddSuggestionsFromListValue(
                   /*content_suggestions_api=*/true, remote_category_id,
-                  *suggestions_list, &suggestions)) {
+                  *suggestions_list, &suggestions, fetch_time)) {
             return false;
           }
         }