Log operator code histogram on new metric log

chrome/browser/metrics/metrics_service.cc

 // Copyright (c) 2012 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 1102 matching lines @@
 void MetricsService::ReceivedProfilerData(
     const tracked_objects::ProcessDataSnapshot& process_data,
     int process_type) {
   DCHECK_EQ(INIT_TASK_SCHEDULED, state_);
 
   // Upon the first callback, create the initial log so that we can immediately
   // save the profiler data.
   if (!initial_metrics_log_.get()) {
     initial_metrics_log_.reset(
         new MetricsLog(client_id_, session_id_, MetricsLog::ONGOING_LOG));
+    NotifyOnNewMetricsLog();
   }
 
   initial_metrics_log_->RecordProfilerData(process_data, process_type);
 }
 
 void MetricsService::FinishedReceivingProfilerData() {
   DCHECK_EQ(INIT_TASK_SCHEDULED, state_);
   state_ = INIT_TASK_DONE;
   scheduler_->InitTaskComplete();
 }
@@ skipping 66 matching lines @@
 
   UMA_HISTOGRAM_BOOLEAN("UMA.GeneratedLowEntropySource", true);
   low_entropy_source_ = GenerateLowEntropySource();
   local_state->SetInteger(prefs::kMetricsLowEntropySource, low_entropy_source_);
   local_state->ClearPref(prefs::kMetricsOldLowEntropySource);
   metrics::CachingPermutedEntropyProvider::ClearCache(local_state);
 
   return low_entropy_source_;
 }
 
+void MetricsService::AddMetricsLogObserver(MetricsLogObserver* observer) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  metrics_log_observers_.AddObserver(observer);
+}
+
+void MetricsService::RemoveMetricsLogObserver(MetricsLogObserver* observer) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  metrics_log_observers_.RemoveObserver(observer);

[bengr, 2014/05/06 17:14:39]

Are the observers guaranteed to outlive the MetricsService?

[bolian, 2014/05/06 18:00:08]

For the current usage, Yes.
If not in the future, observers should remove themselves before die.

+}
+
+void MetricsService::NotifyOnNewMetricsLog() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  FOR_EACH_OBSERVER(
+      MetricsLogObserver, metrics_log_observers_, OnNewMetricsLog());
+}
+
 // static
 std::string MetricsService::GenerateClientID() {
   return base::GenerateGUID();
 }
 
 //------------------------------------------------------------------------------
 // State save methods
 
 void MetricsService::ScheduleNextStateSave() {
   state_saver_factory_.InvalidateWeakPtrs();
@@ skipping 19 matching lines @@
 
 
 //------------------------------------------------------------------------------
 // Recording control methods
 
 void MetricsService::OpenNewLog() {
   DCHECK(!log_manager_.current_log());
 
   log_manager_.BeginLoggingWithLog(
       new MetricsLog(client_id_, session_id_, MetricsLog::ONGOING_LOG));
+  NotifyOnNewMetricsLog();
   if (state_ == INITIALIZED) {
     // We only need to schedule that run once.
     state_ = INIT_TASK_SCHEDULED;
 
     // Schedules a task on the file thread for execution of slower
     // initialization steps (such as plugin list generation) necessary
     // for sending the initial log.  This avoids blocking the main UI
     // thread.
     BrowserThread::PostDelayedTask(
         BrowserThread::FILE,
@@ skipping 277 matching lines @@
 }
 
 void MetricsService::PrepareInitialStabilityLog() {
   DCHECK_EQ(INITIALIZED, state_);
   PrefService* pref = g_browser_process->local_state();
   DCHECK_NE(0, pref->GetInteger(prefs::kStabilityCrashCount));
 
   scoped_ptr<MetricsLog> initial_stability_log(
       new MetricsLog(client_id_, session_id_,
                      MetricsLog::INITIAL_STABILITY_LOG));
+  NotifyOnNewMetricsLog();
   if (!initial_stability_log->LoadSavedEnvironmentFromPrefs())
     return;
   initial_stability_log->RecordStabilityMetrics(base::TimeDelta(),
                                                 base::TimeDelta());
   log_manager_.LoadPersistedUnsentLogs();
 
   log_manager_.PauseCurrentLog();
   log_manager_.BeginLoggingWithLog(initial_stability_log.release());
 #if defined(OS_ANDROID)
   ConvertAndroidStabilityPrefsToHistograms(pref);
@@ skipping 520 matching lines @@
   // Android has its own settings for metrics / crash uploading.
   const PrefService* prefs = g_browser_process->local_state();
   return prefs->GetBoolean(prefs::kCrashReportingEnabled);
 #else
   return MetricsServiceHelper::IsMetricsReportingEnabled();
 #endif
 #else
   return false;
 #endif
 }
+
+void MetricsServiceHelper::AddMetricsLogObserver(
+    MetricsLogObserver* observer) {
+  MetricsService* metrics_service = g_browser_process->metrics_service();
+  if (metrics_service != NULL) {

[bengr, 2014/05/06 17:14:39]

When would this be null?

[bolian, 2014/05/06 18:00:08]

Just as a safety check before dereferring it. In theory, an observer could call
MetricsServiceHelper::AddMetricsLogObserver before the metrics service created.
But not for this CL. 

+    metrics_service->AddMetricsLogObserver(observer);
+  }
+}
+
+void MetricsServiceHelper::RemoveMetricsLogObserver(
+    MetricsLogObserver* observer) {
+  MetricsService* metrics_service = g_browser_process->metrics_service();
+  if (metrics_service != NULL) {
+    metrics_service->RemoveMetricsLogObserver(observer);
+  }
+}