Add Statistics for SupervisedUserSettingService during merging and syncing data.

chrome/browser/supervised_user/legacy/supervised_user_shared_settings_service.cc

Index: chrome/browser/supervised_user/legacy/supervised_user_shared_settings_service.cc
diff --git a/chrome/browser/supervised_user/legacy/supervised_user_shared_settings_service.cc b/chrome/browser/supervised_user/legacy/supervised_user_shared_settings_service.cc
index 60ec741691a6160e6fb02412b393bfb035aeac18..722eb1fad6bbe0a205eb4b3be87ad658379eb091 100644
--- a/chrome/browser/supervised_user/legacy/supervised_user_shared_settings_service.cc
+++ b/chrome/browser/supervised_user/legacy/supervised_user_shared_settings_service.cc
@@ -10,6 +10,7 @@
 
 #include "base/json/json_reader.h"
 #include "base/json/json_writer.h"
+#include "base/metrics/histogram.h"
 #include "base/prefs/pref_service.h"
 #include "base/prefs/scoped_user_pref_update.h"
 #include "base/values.h"
@@ -259,7 +260,9 @@ SupervisedUserSharedSettingsService::MergeDataAndStartSyncing(
         sync_processor_->ProcessSyncChanges(FROM_HERE, change_list));
   }
 
-  // TODO(bauerb): Statistics?

[Bernhard Bauer, 2016/01/04 12:53:30]

Sorry, that comment should have been more detailed 😃 The statistics mentioned
here are statistics about the merge result, i.e. things like the number of items
that were added, deleted, updated, etc. (see the API of SyncMergeResult for
details), not UMA histograms.

[Deepak, 2016/01/05 03:45:16]

Done.

+  UMA_HISTOGRAM_ENUMERATION("SupervisedUserSettingService.SyncMergeResult",
+                            result.model_type(), syncer::MODEL_TYPE_COUNT);
+
   return result;
 }