[Sync] DeviceInfo implementation of MergeSyncData.

components/sync_driver/device_info_service.cc

Index: components/sync_driver/device_info_service.cc
diff --git a/components/sync_driver/device_info_service.cc b/components/sync_driver/device_info_service.cc
index 1049ede177b58a96b9ca0b05a0ab412e7c140242..639197e9af33d030d3e6c2c54e36bbd522ff8723 100644
--- a/components/sync_driver/device_info_service.cc
+++ b/components/sync_driver/device_info_service.cc
@@ -4,6 +4,7 @@
 
 #include "components/sync_driver/device_info_service.h"
 
+#include <set>
 #include <utility>
 #include <vector>
 
@@ -25,6 +26,7 @@ using syncer_v2::EntityChange;
 using syncer_v2::EntityChangeList;
 using syncer_v2::EntityData;
 using syncer_v2::EntityDataList;
+using syncer_v2::EntityDataPtr;
 using syncer_v2::MetadataBatch;
 using syncer_v2::MetadataChangeList;
 using syncer_v2::ModelTypeStore;
@@ -69,8 +71,54 @@ scoped_ptr<MetadataChangeList> DeviceInfoService::CreateMetadataChangeList() {
 SyncError DeviceInfoService::MergeSyncData(
     scoped_ptr<MetadataChangeList> metadata_change_list,
     EntityDataList entity_data_list) {
-  // TODO(skym): crbug.com/543406: Implementation.
-  return SyncError();
+  if (!has_provider_initialized_ || !has_data_loaded_ || !change_processor()) {
+    return SyncError(
+        FROM_HERE, SyncError::DATATYPE_ERROR,
+        "Cannot call MergeSyncData without provider, data, and processor.",
+        syncer::DEVICE_INFO);
+  }
+
+  // Local data should typically be near empty, with the only possible value
+  // corresponding to this device. This is because on signout all device info
+  // data is blown away. However, this simplification is being ignored here and
+  // a full difference is going to be calculated to explore what other service
+  // implementations may look like.
+  std::set<std::string> local_only_tags;
+  for (auto& kv : all_data_) {

[maxbogue, 2016/02/23 01:04:02]

"const auto&"?

[skym, 2016/03/04 20:28:10]

Done.

+    local_only_tags.insert(kv.first);
+  }
+
+  std::string local_tag =
+      local_device_info_provider_->GetLocalDeviceInfo()->guid();
+  scoped_ptr<WriteBatch> batch = store_->CreateWriteBatch();
+  for (EntityDataPtr& entity_data_ptr : entity_data_list) {

[maxbogue, 2016/02/23 01:04:02]

"const EntityDataPtr&"?

[skym, 2016/03/04 20:28:10]

Done.

+    const std::string tag = GetClientTag(entity_data_ptr.value());
+    const DeviceInfoSpecifics& specifics =
+        entity_data_ptr.value().specifics.device_info();
+
+    // Ignore any remote changes that have our local cache guid.
+    if (tag == local_tag) {
+      continue;
+    }
+
+    // Remote data wins conflicts.
+    local_only_tags.erase(tag);
+    StoreSpecifics(make_scoped_ptr(new DeviceInfoSpecifics(specifics)),
+                   batch.get());
+  }
+
+  for (const std::string& tag : local_only_tags) {
+    change_processor()->Put(tag, CopyIntoNewEntityData(*all_data_[tag].get()),

[maxbogue, 2016/02/23 01:04:02]

Nit: pretty sure the .get() is superfluous here and you can just deref a
scoped_ptr.

[skym, 2016/03/04 20:28:10]

TIL. Done.

+                            metadata_change_list.get());
+  }
+
+  // Transfer at the end because processor Put calls may update metadata.
+  static_cast<SimpleMetadataChangeList*>(metadata_change_list.get())
+      ->TransferChanges(store_.get(), batch.get());
+  store_->CommitWriteBatch(
+      std::move(batch),
+      base::Bind(&DeviceInfoService::OnCommit, weak_factory_.GetWeakPtr()));

[skym, 2016/02/22 17:43:10]

Should be calling NotifyObservers(); at the end of this function if any change
occurred.

[skym, 2016/03/04 20:28:10]

Done.

+  return syncer::SyncError();
 }
 
 SyncError DeviceInfoService::ApplySyncChanges(