[Sync] Implements the loopback sync server.

components/sync/engine_impl/loopback_server/loopback_connection_manager.cc

+// Copyright 2016 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 "components/sync/engine_impl/loopback_server/loopback_connection_manager.h"
+
+#include <string>
+
+namespace syncer {
+
+LoopbackConnectionManager::LoopbackConnectionManager(
+    CancelationSignal* signal,
+    const base::FilePath& persistent_file)
+    : ServerConnectionManager("localhost", 0, false, signal),
+      loopback_server_(persistent_file) {}
+
+LoopbackConnectionManager::~LoopbackConnectionManager() {}
+
+bool LoopbackConnectionManager::PostBufferToPath(
+    PostBufferParams* params,
+    const std::string& path,
+    const std::string& auth_token) {
+  loopback_server_.HandleCommand(
+      params->buffer_in, &params->response.server_status,
+      &params->response.response_code, &params->buffer_out);
+  return params->response.server_status == HttpResponse::SERVER_CONNECTION_OK;
+}
+
+}  // namespace syncer