[NTP Snippets] Cleanups from clang-tidy

components/ntp_snippets/user_classifier.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/user_classifier.h"
 
-#include <float.h>
-
 #include <algorithm>
+#include <cfloat>
 #include <string>
 
 #include "base/metrics/histogram_macros.h"
 #include "base/strings/string_number_conversions.h"
 #include "components/ntp_snippets/features.h"
 #include "components/ntp_snippets/pref_names.h"
 #include "components/prefs/pref_registry_simple.h"
 #include "components/prefs/pref_service.h"
 #include "components/variations/variations_associated_data.h"
 
@@ skipping 188 matching lines @@
   // differs from the previous value, rescale the metric values so that the
   // expectation does not change abruptly!
 
   // Initialize the prefs storing the last time: the counter has just started!
   for (const Metric metric : kMetrics) {
     if (!HasLastTime(metric))
       SetLastTimeToNow(metric);
   }
 }
 
-UserClassifier::~UserClassifier() {}
+UserClassifier::~UserClassifier() = default;
 
 // static
 void UserClassifier::RegisterProfilePrefs(PrefRegistrySimple* registry) {
   double discount_rate = GetDiscountRatePerHour();
   double min_hours = GetMinHours();
   double max_hours = GetMaxHours();
 
   for (Metric metric : kMetrics) {
     double default_metric_value = GetMetricValueForEstimateHoursBetweenEvents(
         GetInitialHoursBetweenEvents(metric), discount_rate, min_hours,
@@ skipping 136 matching lines @@
 
 void UserClassifier::SetMetricValue(Metric metric, double metric_value) {
   pref_service_->SetDouble(kMetricKeys[static_cast<int>(metric)], metric_value);
 }
 
 void UserClassifier::ClearMetricValue(Metric metric) {
   pref_service_->ClearPref(kMetricKeys[static_cast<int>(metric)]);
 }
 
 }  // namespace ntp_snippets