Log the sync communication that happens between client and server.

sync/protocol/proto_value_conversions.h

 // Copyright (c) 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.
 
 // Keep this file in sync with the .proto files in this directory.
 
 #ifndef SYNC_PROTOCOL_PROTO_VALUE_CONVERSIONS_H_
 #define SYNC_PROTOCOL_PROTO_VALUE_CONVERSIONS_H_
 #pragma once
 
 namespace base {
 class DictionaryValue;
 }
 
 namespace sync_pb {
 class AppNotification;
 class AppNotificationSettings;
 class AppSettingSpecifics;
 class AppSpecifics;
 class AutofillProfileSpecifics;
 class AutofillSpecifics;
 class BookmarkSpecifics;
+class ClientToServerMessage;
+class ClientToServerResponse;
 class DeviceInformation;
 class EncryptedData;
 class EntitySpecifics;
 class ExtensionSettingSpecifics;
 class ExtensionSpecifics;
 class NigoriSpecifics;
 class PasswordSpecifics;
 class PasswordSpecificsData;
 class PreferenceSpecifics;
 class SearchEngineSpecifics;
@@ skipping 97 matching lines @@
     const sync_pb::ThemeSpecifics& theme_specifics);
 
 base::DictionaryValue* TypedUrlSpecificsToValue(
     const sync_pb::TypedUrlSpecifics& typed_url_specifics);
 
 // Any present extensions are mapped to sub-dictionary values with the
 // key equal to the extension name.
 base::DictionaryValue* EntitySpecificsToValue(
     const sync_pb::EntitySpecifics& specifics);
 
+base::DictionaryValue* ClientToServerMessageToValue(
+    const sync_pb::ClientToServerMessage& proto,
+    bool include_specifics);
+
+base::DictionaryValue* ClientToServerResponseToValue(
+    const sync_pb::ClientToServerResponse& proto,
+    bool include_specifics);
+
+
 }  // namespace browser_sync
 
 #endif  // SYNC_PROTOCOL_PROTO_VALUE_CONVERSIONS_H_