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

components/metrics/metrics_service.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.
 
 //------------------------------------------------------------------------------
 // Description of the life cycle of a instance of MetricsService.
 //
 //  OVERVIEW
 //
 // A MetricsService instance is typically created at application startup.  It is
@@ skipping 505 matching lines @@
     IncrementPrefValue(prefs::kStabilityDebuggerNotPresent);
   else
     IncrementPrefValue(prefs::kStabilityDebuggerPresent);
 }
 
 void MetricsService::ClearSavedStabilityMetrics() {
   for (MetricsProvider* provider : metrics_providers_)
     provider->ClearSavedStabilityMetrics();
 
   // Reset the prefs that are managed by MetricsService/MetricsLog directly.
+  local_state_->SetInteger(prefs::kStabilityBreakpadRegistrationSuccess, 0);
+  local_state_->SetInteger(prefs::kStabilityBreakpadRegistrationFail, 0);
   local_state_->SetInteger(prefs::kStabilityCrashCount, 0);
+  local_state_->SetInteger(prefs::kStabilityDebuggerPresent, 0);
+  local_state_->SetInteger(prefs::kStabilityDebuggerNotPresent, 0);
   local_state_->SetInteger(prefs::kStabilityExecutionPhase,
                            UNINITIALIZED_PHASE);
   local_state_->SetInteger(prefs::kStabilityIncompleteSessionEndCount, 0);
   local_state_->SetInteger(prefs::kStabilityLaunchCount, 0);
   local_state_->SetBoolean(prefs::kStabilitySessionEndCompleted, true);
 }
 
 void MetricsService::PushExternalLog(const std::string& log) {
   log_manager_.StoreLog(log, MetricsLog::ONGOING_LOG);
 }
@@ skipping 667 matching lines @@
                  base::Time::Now().ToTimeT());
 }
 
 void MetricsService::SkipAndDiscardUpload() {
   log_manager_.DiscardStagedLog();
   scheduler_->UploadCancelled();
   log_upload_in_progress_ = false;
 }
 
 }  // namespace metrics