Clear client id prefs when opting out of UMA.

chrome/browser/metrics/metrics_reporting_state.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.
 
 #include "chrome/browser/metrics/metrics_reporting_state.h"
 
 #include "base/callback.h"
 #include "base/metrics/histogram.h"
 #include "build/build_config.h"
 #include "chrome/browser/browser_process.h"
@@ skipping 49 matching lines @@
 void SetMetricsReporting(bool to_update_pref,
                          const OnMetricsReportingCallbackType& callback_fn,
                          bool updated_pref) {
   metrics::MetricsService* metrics = g_browser_process->metrics_service();
 
 #if !defined(OS_ANDROID)
   g_browser_process->local_state()->SetBoolean(
       metrics::prefs::kMetricsReportingEnabled, updated_pref);
 #endif  // !defined(OS_ANDROID)
 
-  // Uses the current state of whether reporting is enabled to enabled services.
+  // Clear the client id pref when opting out. Note: Mirrors code in
+  // uma_session_stats.cc. TODO(asvitkine): Unify.
+  if (!updated_pref) {
+    // Note: Clearing client id will not affect the running state (e.g. field
+    // trial randomization), as the pref is only read on startup.
+    g_browser_process->local_state()->ClearPref(
+        metrics::prefs::kMetricsClientID);
+    g_browser_process->local_state()->ClearPref(
+        metrics::prefs::kMetricsReportingEnabledTimestamp);
+  }
+
+  // Uses the current state of whether reporting is enabled to enable services.
   g_browser_process->GetMetricsServicesManager()->UpdateUploadPermissions(true);
 
   // When a user opts in to the metrics reporting service, the previously
   // collected data should be cleared to ensure that nothing is reported before
   // a user opts in and all reported data is accurate.
+  // TODO(asvitkine): This logic should be added to uma_session_stats.cc too.
   if (updated_pref && metrics)
     metrics->ClearSavedStabilityMetrics();
 
   if (to_update_pref == updated_pref) {
     RecordMetricsReportingHistogramValue(updated_pref ?
         METRICS_REPORTING_ENABLED : METRICS_REPORTING_DISABLED);
   } else {
     RecordMetricsReportingHistogramValue(METRICS_REPORTING_ERROR);
   }
   if (!callback_fn.is_null())
@@ skipping 51 matching lines @@
 // will trigger this function and kMetricsReportinEnabled as well as metrics
 // service state will be updated accordingly.
 void SetupMetricsStateForChromeOS() {
 #if defined(OS_CHROMEOS)
   chromeos::CrosSettings::Get()->AddSettingsObserver(
       chromeos::kStatsReportingPref, base::Bind(&OnDeviceSettingChange));
 
   OnDeviceSettingChange();
 #endif // defined(OS_CHROMEOS)
 }