Allow empty UKM entries to be recorded.

components/ukm/ukm_service_unittest.cc

 // 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.
 
 #include "components/ukm/ukm_service.h"
 
 #include <map>
 #include <string>
 #include <utility>
 
@@ skipping 241 matching lines @@
   EXPECT_EQ(2, proto_entry_foo.metrics_size());
   const Entry::Metric proto_entry_foo_start = proto_entry_foo.metrics(0);
   EXPECT_EQ(base::HashMetricName("foo_start"),
             proto_entry_foo_start.metric_hash());
   EXPECT_EQ(0, proto_entry_foo_start.value());
   const Entry::Metric proto_entry_foo_end = proto_entry_foo.metrics(1);
   EXPECT_EQ(base::HashMetricName("foo_end"), proto_entry_foo_end.metric_hash());
   EXPECT_EQ(10, proto_entry_foo_end.value());
 }
 
-TEST_F(UkmServiceTest, AddEntryOnlyWithNonEmptyMetrics) {
+TEST_F(UkmServiceTest, AddEntryWithEmptyMetrics) {
   UkmService service(&prefs_, &client_);
   EXPECT_EQ(0, GetPersistedLogCount());
   service.Initialize();
   task_runner_->RunUntilIdle();
   service.EnableRecording();
   service.EnableReporting();
 
   int32_t id = UkmService::GetNewSourceID();
   service.UpdateSourceURL(id, GURL("https://google.com/foobar"));
 
   {
     std::unique_ptr<UkmEntryBuilder> builder =
         service.GetEntryBuilder(id, "PageLoad");
   }
   service.Flush();
   EXPECT_EQ(1, GetPersistedLogCount());
   Report proto_report = GetPersistedReport();
-  EXPECT_EQ(0, proto_report.entries_size());
-
-  {
-    std::unique_ptr<UkmEntryBuilder> builder =
-        service.GetEntryBuilder(id, "PageLoad");
-    builder->AddMetric("FirstContentfulPaint", 300);
-  }
-  service.Flush();
-  EXPECT_EQ(2, GetPersistedLogCount());
-  Report proto_report_with_entries = GetPersistedReport();
-  EXPECT_EQ(1, proto_report_with_entries.entries_size());
+  EXPECT_EQ(1, proto_report.entries_size());
 }
 
 TEST_F(UkmServiceTest, MetricsProviderTest) {
   UkmService service(&prefs_, &client_);
 
   metrics::TestMetricsProvider* provider = new metrics::TestMetricsProvider();
   service.RegisterMetricsProvider(
       std::unique_ptr<metrics::MetricsProvider>(provider));
 
   service.Initialize();
@@ skipping 257 matching lines @@
   service.Flush();
   EXPECT_EQ(1, GetPersistedLogCount());
 
   auto proto_report = GetPersistedReport();
   ASSERT_EQ(1, proto_report.sources_size());
   const Source& proto_source = proto_report.sources(0);
   EXPECT_EQ("URLTooLong", proto_source.url());
 }
 
 }  // namespace ukm