Avoid some pref writes in MetricsLog. Ensure some stability metrics are cleared.

components/metrics/metrics_log_unittest.cc

 // Copyright 2014 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/metrics/metrics_log.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <string>
@@ skipping 370 matching lines @@
   log.RecordEnvironment(metrics_providers.get(),
                         std::vector<variations::ActiveGroupId>(), kInstallDate,
                         kEnabledDate);
   log.RecordStabilityMetrics(metrics_providers.get(), base::TimeDelta(),
                              base::TimeDelta());
   const SystemProfileProto_Stability& stability =
       log.system_profile().stability();
   // Required metrics:
   EXPECT_TRUE(stability.has_launch_count());
   EXPECT_TRUE(stability.has_crash_count());
-  // Initial log metrics:
-  EXPECT_TRUE(stability.has_incomplete_shutdown_count());
-  EXPECT_TRUE(stability.has_breakpad_registration_success_count());
-  EXPECT_TRUE(stability.has_breakpad_registration_failure_count());
-  EXPECT_TRUE(stability.has_debugger_present_count());
-  EXPECT_TRUE(stability.has_debugger_not_present_count());
+  // Initial log metrics: only expected if non-zero.
+  EXPECT_FALSE(stability.has_incomplete_shutdown_count());
+  EXPECT_FALSE(stability.has_breakpad_registration_success_count());
+  EXPECT_FALSE(stability.has_breakpad_registration_failure_count());
+  EXPECT_FALSE(stability.has_debugger_present_count());
+  EXPECT_FALSE(stability.has_debugger_not_present_count());
 
   // The test provider should have been called upon to provide initial
   // stability and regular stability metrics.
   EXPECT_TRUE(test_provider->provide_initial_stability_metrics_called());
   EXPECT_TRUE(test_provider->provide_stability_metrics_called());
 }
 
 TEST_F(MetricsLogTest, OngoingLogStabilityMetrics) {
   TestMetricsServiceClient client;
   TestMetricsLog log(
       kClientId, kSessionId, MetricsLog::ONGOING_LOG, &client, &prefs_);
   TestMetricsProvider* test_provider = new TestMetricsProvider();
   ScopedVector<MetricsProvider> metrics_providers;
   metrics_providers.push_back(test_provider);
   log.RecordEnvironment(metrics_providers.get(),
                         std::vector<variations::ActiveGroupId>(), kInstallDate,
                         kEnabledDate);
   log.RecordStabilityMetrics(metrics_providers.get(), base::TimeDelta(),
                              base::TimeDelta());
   const SystemProfileProto_Stability& stability =
       log.system_profile().stability();
   // Required metrics:
   EXPECT_TRUE(stability.has_launch_count());
   EXPECT_TRUE(stability.has_crash_count());
-  // Initial log metrics:
+  // Initial log metrics: only expected if non-zero.
   EXPECT_FALSE(stability.has_incomplete_shutdown_count());
   EXPECT_FALSE(stability.has_breakpad_registration_success_count());
   EXPECT_FALSE(stability.has_breakpad_registration_failure_count());
   EXPECT_FALSE(stability.has_debugger_present_count());
   EXPECT_FALSE(stability.has_debugger_not_present_count());
 
   // The test provider should have been called upon to provide regular but not
   // initial stability metrics.
   EXPECT_FALSE(test_provider->provide_initial_stability_metrics_called());
   EXPECT_TRUE(test_provider->provide_stability_metrics_called());
@@ skipping 24 matching lines @@
   TestMetricsServiceClient client;
   client.set_product(kTestProduct);
   TestMetricsLog log(
       kClientId, kSessionId, MetricsLog::ONGOING_LOG, &client, &prefs_);
   // Check that the product is set to |kTestProduct|.
   EXPECT_TRUE(log.uma_proto().has_product());
   EXPECT_EQ(kTestProduct, log.uma_proto().product());
 }
 
 }  // namespace metrics