[remote suggestions] Add a new histogram for recording the time since a snippet was fetched.

components/ntp_snippets/content_suggestions_metrics.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/ntp_snippets/content_suggestions_metrics.h"
 
 #include <cmath>
 #include <string>
 #include <type_traits>
 
@@ skipping 41 matching lines @@
 const char kHistogramVisitDuration[] =
     "NewTabPage.ContentSuggestions.VisitDuration";
 const char kHistogramMoreButtonShown[] =
     "NewTabPage.ContentSuggestions.MoreButtonShown";
 const char kHistogramMoreButtonClicked[] =
     "NewTabPage.ContentSuggestions.MoreButtonClicked";
 const char kHistogramMovedUpCategoryNewIndex[] =
     "NewTabPage.ContentSuggestions.MovedUpCategoryNewIndex";
 const char kHistogramCategoryDismissed[] =
     "NewTabPage.ContentSuggestions.CategoryDismissed";
-const char kHistogramContentSuggestionsTimeSinceLastBackgroundFetch[] =
-    "NewTabPage.ContentSuggestions.TimeSinceLastBackgroundFetch";
+const char kHistogramTimeSinceSuggestionFetched[] =
+    "NewTabPage.ContentSuggestions.TimeSinceSuggestionFetched";
 
 const char kPerCategoryHistogramFormat[] = "%s.%s";
 
 // This mostly corresponds to the KnownCategories enum, but it is contiguous
 // and contains exactly the values to be recorded in UMA. Don't remove or
 // reorder elements, only add new ones at the end (before COUNT), and keep in
 // sync with ContentSuggestionsCategory in histograms.xml.
 enum HistogramCategories {
   EXPERIMENTAL,
   RECENT_TABS,
@@ skipping 154 matching lines @@
   UMA_HISTOGRAM_EXACT_LINEAR(kHistogramShown, global_position,
                              kMaxSuggestionsTotal);
   LogCategoryHistogramPosition(kHistogramShown, category, position_in_category,
                                kMaxSuggestionsPerCategory);
 
   base::TimeDelta age = base::Time::Now() - publish_date;
   LogCategoryHistogramAge(kHistogramShownAge, category, age);
 
   LogCategoryHistogramScore(kHistogramShownScore, category, score);
 
+  if (category.IsKnownCategory(KnownCategories::ARTICLES)) {
+    // Records the time since the fetch time of the displayed snippet.
+    UMA_HISTOGRAM_CUSTOM_TIMES(
+        kHistogramTimeSinceSuggestionFetched, base::Time::Now() - fetch_date,
+        base::TimeDelta::FromDays(0), base::TimeDelta::FromDays(7),

[Marc Treib, 2017/02/22 13:38:11]

I think the min value can't be 0. FromSeconds(1)?

[markusheintz_, 2017/02/22 13:42:04]

done. already uploaded. sry I forgot

+        /*bucket_count=*/100);
+  }
+
   // TODO(markusheintz): Discuss whether the code below should be move into a
   // separate method called OnSuggestionsListShown.
   // When the first of the articles suggestions is shown, then we count this as
   // a single usage of content suggestions.
   if (category.IsKnownCategory(KnownCategories::ARTICLES) &&
       position_in_category == 0) {
     RecordContentSuggestionsUsage();
-
-    // Records the time since the last background fetch of the remote content
-    // suggestions.
-    UMA_HISTOGRAM_CUSTOM_TIMES(
-        kHistogramContentSuggestionsTimeSinceLastBackgroundFetch,
-        base::Time::Now() - fetch_date, base::TimeDelta::FromSeconds(1),
-        base::TimeDelta::FromDays(7),
-        /*bucket_count=*/100);
   }
 }
 
 void OnSuggestionOpened(int global_position,
                         Category category,
                         int category_index,
                         int position_in_category,
                         base::Time publish_date,
                         float score,
                         WindowOpenDisposition disposition) {
@@ skipping 89 matching lines @@
 }
 
 void OnCategoryDismissed(Category category) {
   UMA_HISTOGRAM_ENUMERATION(kHistogramCategoryDismissed,
                             GetHistogramCategory(category),
                             HistogramCategories::COUNT);
 }
 
 }  // namespace metrics
 }  // namespace ntp_snippets