[SyncFS] Migrate ServiceMetadata from MDDB to MDDBIndex.

chrome/browser/sync_file_system/drive_backend/drive_backend_util.cc

Index: chrome/browser/sync_file_system/drive_backend/drive_backend_util.cc
diff --git a/chrome/browser/sync_file_system/drive_backend/drive_backend_util.cc b/chrome/browser/sync_file_system/drive_backend/drive_backend_util.cc
index ac9d0d0581e26af57b37e233b5c7775045c09e98..4390b17f401a6cd394b9235b0815836d3c371aa5 100644
--- a/chrome/browser/sync_file_system/drive_backend/drive_backend_util.cc
+++ b/chrome/browser/sync_file_system/drive_backend/drive_backend_util.cc
@@ -8,12 +8,14 @@
 #include "base/memory/scoped_vector.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
+#include "base/threading/thread_restrictions.h"
 #include "chrome/browser/drive/drive_api_util.h"
 #include "chrome/browser/sync_file_system/drive_backend/drive_backend_constants.h"
 #include "chrome/browser/sync_file_system/drive_backend/metadata_database.pb.h"
 #include "chrome/browser/sync_file_system/logger.h"
 #include "google_apis/drive/drive_api_parser.h"
 #include "google_apis/drive/gdata_wapi_parser.h"
+#include "third_party/leveldatabase/src/include/leveldb/db.h"
 #include "third_party/leveldatabase/src/include/leveldb/write_batch.h"
 
 namespace sync_file_system {
@@ -161,5 +163,40 @@ bool RemovePrefix(const std::string& str, const std::string& prefix,
   return true;
 }
 
+scoped_ptr<ServiceMetadata> ReadServiceMetadata(leveldb::DB* db) {
+  base::ThreadRestrictions::AssertIOAllowed();
+  DCHECK(db);
+
+  std::string value;
+  leveldb::Status status = db->Get(leveldb::ReadOptions(),
+                                   kServiceMetadataKey,
+                                   &value);
+  if (!status.ok())
+    return scoped_ptr<ServiceMetadata>();
+
+  scoped_ptr<ServiceMetadata> service_metadata(new ServiceMetadata);
+  if (!service_metadata->ParseFromString(value)) {
+    util::Log(logging::LOG_WARNING, FROM_HERE,
+              "Failed to parse SyncServiceMetadata");
+    return scoped_ptr<ServiceMetadata>();
+  }
+  return service_metadata.Pass();
+}
+
+scoped_ptr<ServiceMetadata> InitializeServiceMetadata(
+    leveldb::DB* db, leveldb::WriteBatch* batch) {
+  scoped_ptr<ServiceMetadata> service_metadata = ReadServiceMetadata(db);
+  if (!service_metadata) {
+    service_metadata.reset(new ServiceMetadata);
+    service_metadata->set_next_tracker_id(1);
+
+    std::string value;
+    service_metadata->SerializeToString(&value);
+    if (batch)
+      batch->Put(kServiceMetadataKey, value);

[nhiroki, 2014/07/15 07:47:20]

Is it necessary to put the initial metadata here? I wonder if the index puts it
when actually using it.

[peria, 2014/07/15 09:00:58]

Hmm, it sounds acceptable to remove handling |batch| here.

+  }
+  return service_metadata.Pass();
+}
+
 }  // namespace drive_backend
 }  // namespace sync_file_system