sync: Move unique_client_tag hashing code

sync/syncable/syncable_util.cc

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "sync/syncable/syncable_util.h"
 
+#include "base/base64.h"
 #include "base/location.h"
 #include "base/logging.h"
+#include "base/sha1.h"
 #include "sync/syncable/directory.h"
 #include "sync/syncable/entry.h"
 #include "sync/syncable/mutable_entry.h"
 #include "sync/syncable/syncable_id.h"
 #include "sync/syncable/syncable_write_transaction.h"
 
 namespace syncer {
 namespace syncable {
 
 // Returns the number of unsynced entries.
@@ skipping 76 matching lines @@
                 const tracked_objects::Location& location,
                 const char* msg,
                 BaseTransaction* trans) {
   if (!condition) {
     trans->OnUnrecoverableError(location, msg);
     return false;
   }
   return true;
 }
 
+std::string GenerateSyncableHash(
+    ModelType model_type, const std::string& client_tag) {
+  // Blank PB with just the field in it has termination symbol,
+  // handy for delimiter.
+  sync_pb::EntitySpecifics serialized_type;
+  AddDefaultFieldValue(model_type, &serialized_type);
+  std::string hash_input;
+  serialized_type.AppendToString(&hash_input);
+  hash_input.append(client_tag);
+
+  std::string encode_output;
+  CHECK(base::Base64Encode(base::SHA1HashString(hash_input), &encode_output));
+  return encode_output;
+}
+
 }  // namespace syncable
 }  // namespace syncer