[Part-2]Add Statistics for SupervisedUserSettingService during merging and syncing data.

chrome/browser/supervised_user/supervised_user_settings_service.cc

Index: chrome/browser/supervised_user/supervised_user_settings_service.cc
diff --git a/chrome/browser/supervised_user/supervised_user_settings_service.cc b/chrome/browser/supervised_user/supervised_user_settings_service.cc
index db09106b4e5df4dd6792f75746f69d280395fa07..642205fb64edc0e6820d00770ef938f5ab0b8f85 100644
--- a/chrome/browser/supervised_user/supervised_user_settings_service.cc
+++ b/chrome/browser/supervised_user/supervised_user_settings_service.cc
@@ -193,8 +193,31 @@ SyncMergeResult SupervisedUserSettingsService::MergeDataAndStartSyncing(
   sync_processor_ = std::move(sync_processor);
   error_handler_ = std::move(error_handler);
 
+  std::map<std::string, std::string> seen_keys;
+  int num_before_association = GetAtomicSettings()->size();
+  for (base::DictionaryValue::Iterator it(*GetAtomicSettings()); !it.IsAtEnd();
+       it.Advance()) {
+    std::string json_value;
+    base::JSONWriter::Write(it.value(), &json_value);
+    seen_keys[it.key()] = json_value;
+  }
+  for (base::DictionaryValue::Iterator it(*GetSplitSettings()); !it.IsAtEnd();
+       it.Advance()) {
+    const base::DictionaryValue* dict = nullptr;
+    it.value().GetAsDictionary(&dict);
+    num_before_association += dict->size();
+    for (base::DictionaryValue::Iterator jt(*dict); !jt.IsAtEnd();
+         jt.Advance()) {
+      std::string json_value;
+      base::JSONWriter::Write(jt.value(), &json_value);

[Bernhard Bauer, 2016/01/08 16:04:46]

You serialize the values and then compare them below. What you could do instead
is to store the unserialized base::Value's and compare them to the deserialized
ones from Sync (which you already have), so you don't have to do any additional
serialization.

[Deepak, 2016/01/11 10:38:36]

Done.

+      seen_keys[MakeSplitSettingKey(it.key(), jt.key())] = json_value;
+    }
+  }
+
   // Clear all atomic and split settings, then recreate them from Sync data.
   Clear();
+  int num_added = 0;
+  int num_modified = 0;
   for (const SyncData& sync_data : initial_sync_data) {
     DCHECK_EQ(SUPERVISED_USER_SETTINGS, sync_data.GetDataType());
     const ::sync_pb::ManagedUserSettingSpecifics& supervised_user_setting =
@@ -202,9 +225,22 @@ SyncMergeResult SupervisedUserSettingsService::MergeDataAndStartSyncing(
     scoped_ptr<base::Value> value =
         JSONReader::Read(supervised_user_setting.value());
     std::string name_suffix = supervised_user_setting.name();
+    std::string name_key = name_suffix;
     base::DictionaryValue* dict = GetDictionaryAndSplitKey(&name_suffix);
     dict->SetWithoutPathExpansion(name_suffix, value.release());
+
+    if (seen_keys.find(name_key) == seen_keys.end()) {
+      num_added++;
+    } else {
+      for (DictionaryValue::Iterator jt(*dict); !jt.IsAtEnd(); jt.Advance()) {
+        std::string json_value;

[Bernhard Bauer, 2016/01/08 16:04:46]

This is identical to supervised_user_setting.value() anyway. (But see my comment
above for comparing the base::Value's.)

[Deepak, 2016/01/11 10:38:36]

Done.

+        base::JSONWriter::Write(jt.value(), &json_value);
+        if (seen_keys[name_key] != json_value)
+          num_modified++;
+      }
+    }
   }
+
   store_->ReportValueChanged(kAtomicSettings,
                              WriteablePrefStore::DEFAULT_PREF_WRITE_FLAGS);
   store_->ReportValueChanged(kSplitSettings,
@@ -237,7 +273,11 @@ SyncMergeResult SupervisedUserSettingsService::MergeDataAndStartSyncing(
         sync_processor_->ProcessSyncChanges(FROM_HERE, change_list));
   }
 
-  // TODO(bauerb): Statistics?
+  result.set_num_items_added(num_added);
+  result.set_num_items_modified(num_modified);
+  result.set_num_items_deleted(num_before_association - num_modified);
+  result.set_num_items_before_association(num_before_association);
+  result.set_num_items_after_association(GetAllSyncData(type).size());

[Bernhard Bauer, 2016/01/08 16:04:46]

This is clever, but I'm a bit wary that this does more work than necessary, as
it creates all theses Sync items that we don't really use (we just count them).
It might be easier to just count them directly.

[Deepak, 2016/01/11 10:38:36]

Done.

   return result;
 }