Allow empty UKM entries to be recorded.

components/ukm/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_UKM_SERVICE_H_
 #define COMPONENTS_UKM_UKM_SERVICE_H_
 
 #include <stddef.h>
 #include <memory>
 #include <vector>
@@ skipping 104 matching lines @@
   const std::vector<std::unique_ptr<UkmEntry>>& entries_for_testing() const {
     return entries_;
   }
 
  private:
   friend autofill::AutofillMetrics;
   friend payments::JourneyLogger;
   friend PluginInfoMessageFilter;
   friend UkmPageLoadMetricsObserver;
   friend translate::TranslateRankerImpl;
-  FRIEND_TEST_ALL_PREFIXES(UkmServiceTest, AddEntryOnlyWithNonEmptyMetrics);
+  FRIEND_TEST_ALL_PREFIXES(UkmServiceTest, AddEntryWithEmptyMetrics);
   FRIEND_TEST_ALL_PREFIXES(UkmServiceTest, EntryBuilderAndSerialization);
   FRIEND_TEST_ALL_PREFIXES(UkmServiceTest,
                            LogsUploadedOnlyWhenHavingSourcesOrEntries);
   FRIEND_TEST_ALL_PREFIXES(UkmServiceTest, MetricsProviderTest);
   FRIEND_TEST_ALL_PREFIXES(UkmServiceTest, PersistAndPurge);
   FRIEND_TEST_ALL_PREFIXES(UkmServiceTest, WhitelistEntryTest);
 
   // Get a new UkmEntryBuilder object for the specified source ID and event,
   // which can get metrics added to.
   //
@@ skipping 70 matching lines @@
   // Weak pointers factory used to post task on different threads. All weak
   // pointers managed by this factory have the same lifetime as UkmService.
   base::WeakPtrFactory<UkmService> self_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(UkmService);
 };
 
 }  // namespace ukm
 
 #endif  // COMPONENTS_UKM_UKM_SERVICE_H_