Mojo C++ bindings: change some std::unique_ptr<base::Lock> to base::Optional<base::Lock>.

mojo/public/cpp/bindings/lib/multiplex_router.h

 // Copyright 2015 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.
 
 #ifndef MOJO_PUBLIC_CPP_BINDINGS_LIB_MULTIPLEX_ROUTER_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_LIB_MULTIPLEX_ROUTER_H_
 
 #include <stdint.h>
 
 #include <deque>
 #include <map>
 #include <memory>
 #include <string>
 
 #include "base/compiler_specific.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
+#include "base/optional.h"
 #include "base/single_thread_task_runner.h"
 #include "base/synchronization/lock.h"
 #include "base/threading/thread_checker.h"
 #include "mojo/public/cpp/bindings/associated_group_controller.h"
 #include "mojo/public/cpp/bindings/bindings_export.h"
 #include "mojo/public/cpp/bindings/connector.h"
 #include "mojo/public/cpp/bindings/filter_chain.h"
 #include "mojo/public/cpp/bindings/interface_id.h"
 #include "mojo/public/cpp/bindings/message_header_validator.h"
 #include "mojo/public/cpp/bindings/pipe_control_message_handler.h"
@@ skipping 205 matching lines @@
 
   // Owned by |filters_| below.
   MessageHeaderValidator* header_validator_;
 
   FilterChain filters_;
   Connector connector_;
 
   base::ThreadChecker thread_checker_;
 
   // Protects the following members.
-  // Sets to nullptr in Config::SINGLE_INTERFACE* mode.
-  std::unique_ptr<base::Lock> lock_;
+  // Not set in Config::SINGLE_INTERFACE* mode.
+  mutable base::Optional<base::Lock> lock_;
   PipeControlMessageHandler control_message_handler_;
 
   // NOTE: It is unsafe to call into this object while holding |lock_|.
   PipeControlMessageProxy control_message_proxy_;
 
   std::map<InterfaceId, scoped_refptr<InterfaceEndpoint>> endpoints_;
   uint32_t next_interface_id_value_;
 
   std::deque<std::unique_ptr<Task>> tasks_;
   // It refers to tasks in |tasks_| and doesn't own any of them.
   std::map<InterfaceId, std::deque<Task*>> sync_message_tasks_;
 
   bool posted_to_process_tasks_;
   scoped_refptr<base::SingleThreadTaskRunner> posted_to_task_runner_;
 
   bool encountered_error_;
 
   bool paused_;
 
   bool testing_mode_;
 
   DISALLOW_COPY_AND_ASSIGN(MultiplexRouter);
 };
 
 }  // namespace internal
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_MULTIPLEX_ROUTER_H_