Track when and how a profile is signed out via UMA.

chrome/browser/sync/profile_sync_service.cc

Index: chrome/browser/sync/profile_sync_service.cc
diff --git a/chrome/browser/sync/profile_sync_service.cc b/chrome/browser/sync/profile_sync_service.cc
index cf2ae6ea3dd5f4e3c8695d549d2d14b11a9fdd6b..9e7d689b3ee3ed19e31adf89649ecb9662c37033 100644
--- a/chrome/browser/sync/profile_sync_service.cc
+++ b/chrome/browser/sync/profile_sync_service.cc
@@ -69,6 +69,7 @@
 #include "components/signin/core/browser/about_signin_internals.h"
 #include "components/signin/core/browser/profile_oauth2_token_service.h"
 #include "components/signin/core/browser/signin_manager.h"
+#include "components/signin/core/browser/signin_metrics.h"
 #include "components/sync_driver/change_processor.h"
 #include "components/sync_driver/data_type_controller.h"
 #include "components/sync_driver/pref_names.h"
@@ -1432,8 +1433,10 @@ void ProfileSyncService::OnActionableError(const SyncProtocolError& error) {
 #if !defined(OS_CHROMEOS)
       // On desktop Chrome, sign out the user after a dashboard clear.
       // Skip sign out on ChromeOS/Android.
-      if (!startup_controller_.auto_start_enabled())
+      if (!startup_controller_.auto_start_enabled()) {
+        signin_metrics::LogSignout(signin_metrics::SERVER_FORCED_DISABLE);
         SigninManagerFactory::GetForProfile(profile_)->SignOut();
+      }
 #endif
       break;
     case syncer::ROLLBACK_DONE: