Read later: add metrics tracking read/unread counts on Desktop.

Track two sets of read/unread counts, one when the reading list model
has loaded and one when building a log for the current session using the
DesktopPlatformFeaturesMetricsProvider.

Bug: 1163938
Change-Id: I1b23847e7f209cc2a77b57f0e344d7c9b04c546b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2621914Reviewed-by: Olivier Robin <olivierrobin@chromium.org>
Reviewed-by: Michael Wasserman <msw@chromium.org>
Reviewed-by: Jesse Doherty <jwd@chromium.org>
Commit-Queue: Caroline Rising <corising@chromium.org>
Cr-Commit-Position: refs/heads/master@{#845158}

chrome/browser/metrics/desktop_platform_features_metrics_provider.cc

@@ -4,7 +4,16 @@
 
 #include "chrome/browser/metrics/desktop_platform_features_metrics_provider.h"
 
+#include <vector>
+
+#include "base/feature_list.h"
 #include "base/metrics/histogram_macros.h"
+#include "chrome/browser/browser_process.h"
+#include "chrome/browser/profiles/profile.h"
+#include "chrome/browser/profiles/profile_manager.h"
+#include "chrome/browser/ui/read_later/reading_list_model_factory.h"
+#include "components/reading_list/core/reading_list_model.h"
+#include "components/reading_list/features/reading_list_switches.h"
 #include "ui/native_theme/native_theme.h"
 
 namespace {
@@ -34,4 +43,20 @@ void DesktopPlatformFeaturesMetricsProvider::ProvideCurrentSessionData(
                                           : DarkModeStatus::kLight;
   }
   UMA_HISTOGRAM_ENUMERATION("Browser.DarkModeStatus", status);
+
+  // Record how many items are in the reading list.
+  if (base::FeatureList::IsEnabled(reading_list::switches::kReadLater)) {
+    std::vector<Profile*> profiles =
+        g_browser_process->profile_manager()->GetLoadedProfiles();
+    for (Profile* profile : profiles) {
+      ReadingListModel* model =
+          ReadingListModelFactory::GetForBrowserContext(profile);
+      if (model && model->loaded()) {
+        UMA_HISTOGRAM_COUNTS_1000("ReadingList.Unread.Count.OnUMAUpload",
+                                  model->unread_size());
+        UMA_HISTOGRAM_COUNTS_1000("ReadingList.Read.Count.OnUMAUpload",
+                                  model->size() - model->unread_size());
+      }
+    }
+  }
 }

components/reading_list/core/reading_list_model_impl.cc

@@ -6,6 +6,7 @@
 
 #include "base/bind.h"
 #include "base/check_op.h"
+#include "base/metrics/histogram_functions.h"
 #include "base/strings/string_util.h"
 #include "base/time/clock.h"
 #include "components/prefs/pref_service.h"
@@ -48,6 +49,12 @@ void ReadingListModelImpl::StoreLoaded(
   }
   DCHECK(read_entry_count_ + unread_entry_count_ == entries_->size());
   loaded_ = true;
+
+  base::UmaHistogramCounts1000("ReadingList.Unread.Count.OnModelLoaded",
+                               unread_entry_count_);
+  base::UmaHistogramCounts1000("ReadingList.Read.Count.OnModelLoaded",
+                               read_entry_count_);
+
   for (auto& observer : observers_)
     observer.ReadingListModelLoaded(this);
 }

tools/metrics/histograms/histograms_xml/others/histograms.xml

@@ -12581,6 +12581,24 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
   </summary>
 </histogram>
 
+<histogram name="ReadingList.{ReadStatus}.Count.{Variation}" units="count"
+    expires_after="M92">
+  <owner>corising@chromium.org</owner>
+  <owner>chrome-desktop-ui-sea@google.com</owner>
+  <summary>
+    The number of {ReadStatus} items in the reading list. Recorded {Variation}.
+  </summary>
+  <token key="ReadStatus">
+    <variant name="Read" summary="read"/>
+    <variant name="Unread" summary="unread"/>
+  </token>
+  <token key="Variation">
+    <variant name="OnModelLoaded"
+        summary="when the reading list model is loaded"/>
+    <variant name="OnUMAUpload" summary="every UMA upload"/>
+  </token>
+</histogram>
+
 <histogram name="RecoveryComponent.Event" enum="RecoveryComponentEvent"
     expires_after="M77">
   <owner>robertshield@chromium.org</owner>