Add a instance groups to Connect(), and introduce an Identity struct.

components/leveldb/leveldb_app.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/leveldb/leveldb_app.h"
 
 #include "components/leveldb/leveldb_service_impl.h"
 #include "mojo/shell/public/cpp/connection.h"
 
 namespace leveldb {
 
 LevelDBApp::LevelDBApp() {}
 
 LevelDBApp::~LevelDBApp() {}
 
 void LevelDBApp::Initialize(mojo::Connector* connector,
-                            const std::string& url,
-                            const std::string& user_id,
+                            const mojo::Identity& identity,
                             uint32_t id) {
-  tracing_.Initialize(connector, url);
+  tracing_.Initialize(connector, identity.name());
   service_.reset(new LevelDBServiceImpl);
 }
 
 bool LevelDBApp::AcceptConnection(mojo::Connection* connection) {
   connection->AddInterface<LevelDBService>(this);
   return true;
 }
 
 void LevelDBApp::Create(mojo::Connection* connection,
                         mojo::InterfaceRequest<LevelDBService> request) {
   bindings_.AddBinding(service_.get(), std::move(request));
 }
 
 }  // namespace leveldb