Add UMA for the content suggestions settings

components/ntp_snippets/content_suggestions_service.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_service.h"
 
 #include <algorithm>
 #include <iterator>
 #include <set>
 #include <utility>
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/memory/ptr_util.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/time/default_clock.h"
 #include "base/values.h"
 #include "components/ntp_snippets/pref_names.h"
 #include "components/prefs/pref_registry_simple.h"
 #include "components/prefs/pref_service.h"
 #include "ui/gfx/image/image.h"
 
 namespace ntp_snippets {
@@ skipping 17 matching lines @@
   // Can be null in tests.
   if (signin_manager) {
     signin_observer_.Add(signin_manager);
   }
 
   if (history_service) {
     history_service_observer_.Add(history_service);
   }
 
   RestoreDismissedCategoriesFromPrefs();
+
+  UMA_HISTOGRAM_BOOLEAN(
+      "NewTabPage.ContentSuggestions.Preferences.RemoteSuggestions",
+      IsRemoteSuggestionsServiceEnabled());

[Marc Treib, 2017/04/06 15:39:30]

So far, all the metrics recording code lives in the separate metrics.h/cc files.
Can we stay with that?

[dgn, 2017/04/06 17:28:12]

Done.

 }
 
 ContentSuggestionsService::~ContentSuggestionsService() = default;
 
 void ContentSuggestionsService::Shutdown() {
   remote_suggestions_provider_ = nullptr;
   remote_suggestions_scheduler_ = nullptr;
   suggestions_by_category_.clear();
   providers_by_category_.clear();
   categories_.clear();
@@ skipping 476 matching lines @@
 void ContentSuggestionsService::StoreDismissedCategoriesToPrefs() {
   base::ListValue list;
   for (const auto& category_provider_pair : dismissed_providers_by_category_) {
     list.AppendInteger(category_provider_pair.first.id());
   }
 
   pref_service_->Set(prefs::kDismissedCategories, list);
 }
 
 }  // namespace ntp_snippets