Convert first contentful paint logging to the new UKM client API

components/ukm/test_ukm_service.h

 // Copyright 2017 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.
 
 #ifndef COMPONENTS_UKM_TEST_UKM_SERVICE_H_
 #define COMPONENTS_UKM_TEST_UKM_SERVICE_H_
 
 #include <stddef.h>
 #include <memory>
 
 #include "components/metrics/test_metrics_service_client.h"
 #include "components/prefs/testing_pref_service.h"
 #include "components/ukm/ukm_pref_names.h"
 #include "components/ukm/ukm_service.h"
 
 namespace ukm {
 
 // Wraps an UkmService with additional accessors used for testing.
 class TestUkmService : public UkmService {
  public:
   explicit TestUkmService(PrefService* pref_service);
   ~TestUkmService() override;
 
   size_t sources_count() const { return sources_for_testing().size(); }
   const UkmSource* GetSource(size_t source_num) const;
 
+  size_t entries_count() const { return entries_for_testing().size(); }
+  const UkmEntry* GetEntry(size_t entry_num) const;
+
  private:
   metrics::TestMetricsServiceClient test_metrics_service_client_;
 
   DISALLOW_COPY_AND_ASSIGN(TestUkmService);
 };
 
 // Convenience harness used for testing; creates a TestUkmService and
 // supplies it with a prefs service with a longer lifespan.
 class UkmServiceTestingHarness {
  public:
   UkmServiceTestingHarness();
   virtual ~UkmServiceTestingHarness();
 
   TestUkmService* test_ukm_service() { return test_ukm_service_.get(); }
 
  private:
   TestingPrefServiceSimple test_prefs_;
   std::unique_ptr<TestUkmService> test_ukm_service_;
 
   DISALLOW_COPY_AND_ASSIGN(UkmServiceTestingHarness);
 };
 
 }  // namespace ukm
 
 #endif  // COMPONENTS_UKM_TEST_UKM_SERVICE_H_