Enabled client side sampling for user metrics reporting.

chrome/browser/metrics/metrics_reporting_state.cc

Index: chrome/browser/metrics/metrics_reporting_state.cc
diff --git a/chrome/browser/metrics/metrics_reporting_state.cc b/chrome/browser/metrics/metrics_reporting_state.cc
index 9e74f158f3c558422940129dbb06ffa5a7aaa118..1b748a6ac32d765028873f23f51b2f43bb637299 100644
--- a/chrome/browser/metrics/metrics_reporting_state.cc
+++ b/chrome/browser/metrics/metrics_reporting_state.cc
@@ -13,6 +13,7 @@
 #include "chrome/installer/util/google_update_settings.h"
 #include "components/metrics/metrics_pref_names.h"
 #include "components/metrics/metrics_service.h"
+#include "components/metrics_services_manager/metrics_services_manager.h"
 #include "components/prefs/pref_registry_simple.h"
 #include "components/prefs/pref_service.h"
 #include "content/public/browser/browser_thread.h"
@@ -60,18 +61,15 @@ void SetMetricsReporting(bool to_update_pref,
                          const OnMetricsReportingCallbackType& callback_fn,
                          bool updated_pref) {
   metrics::MetricsService* metrics = g_browser_process->metrics_service();
-  if (metrics) {
-    if (updated_pref)
-      metrics->Start();
-    else
-      metrics->Stop();
-  }
 
 #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.
+  g_browser_process->GetMetricsServicesManager()->UpdateUploadPermissions(true);

[Alexei Svitkine (slow), 2016/07/19 15:23:59]

Shouldn't this be updated_pref value and not |true|?

Can this have a unit test?

[jwd, 2016/07/19 21:21:49]

No, the true refers to the "can upload" permission, which is the android
connection type related stuff. It's the same as
https://cs.chromium.org/chromium/src/chrome/browser/chrome_browser_main.cc?l=807
done on startup.

SetMetricsReporting is only called from  InitiateMetricsReportingChange, which
isn't called on Android. Android settings use a totally different method, and
doesn't actually update the running services.

I had considered having an unsupported platform error at the top of this
function for android, and getting rid of the if !defined block.
Probably yes, I'll do that.

+
   // 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.