Revise system profile prefs clearing

components/metrics/metrics_log.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 <algorithm>
 #include <memory>
@@ skipping 402 matching lines @@
   GetFieldTrialIds(&field_trial_ids);
   WriteFieldTrials(field_trial_ids, system_profile);
   WriteFieldTrials(synthetic_trials, system_profile);
 
   for (size_t i = 0; i < metrics_providers.size(); ++i)
     metrics_providers[i]->ProvideSystemProfileMetrics(system_profile);
 
   std::string serialized_system_profile;
   std::string base64_system_profile;
   if (system_profile->SerializeToString(&serialized_system_profile)) {
+    // Persist the system profile to disk. In the event of an unclean shutdown,
+    // it will be used as part of the initial stability report.
     base::Base64Encode(serialized_system_profile, &base64_system_profile);
     PrefService* local_state = local_state_;
     local_state->SetString(prefs::kStabilitySavedSystemProfile,
                            base64_system_profile);
     local_state->SetString(prefs::kStabilitySavedSystemProfileHash,
                            ComputeSHA1(serialized_system_profile));
   }
 }
 
 bool MetricsLog::LoadSavedEnvironmentFromPrefs(std::string* app_version) {
   DCHECK(app_version);
   app_version->clear();
 
   PrefService* local_state = local_state_;
   const std::string base64_system_profile =
       local_state->GetString(prefs::kStabilitySavedSystemProfile);
   if (base64_system_profile.empty())
     return false;
-
   const std::string system_profile_hash =
       local_state->GetString(prefs::kStabilitySavedSystemProfileHash);
-  local_state->ClearPref(prefs::kStabilitySavedSystemProfile);
-  local_state->ClearPref(prefs::kStabilitySavedSystemProfileHash);
 
   SystemProfileProto* system_profile = uma_proto()->mutable_system_profile();
   std::string serialized_system_profile;
 
   bool success =
       base::Base64Decode(base64_system_profile, &serialized_system_profile) &&
       ComputeSHA1(serialized_system_profile) == system_profile_hash &&
       system_profile->ParseFromString(serialized_system_profile);
   if (success)
     *app_version = system_profile->app_version();
   return success;
 }
 
 void MetricsLog::CloseLog() {
   DCHECK(!closed_);
   closed_ = true;
 }
 
 void MetricsLog::GetEncodedLog(std::string* encoded_log) {
   DCHECK(closed_);
   uma_proto_.SerializeToString(encoded_log);
 }
 
 }  // namespace metrics