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

mojo/public/cpp/bindings/connector.h

 // Copyright 2013 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_CONNECTOR_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_CONNECTOR_H_
 
 #include <memory>
 
 #include "base/callback.h"
 #include "base/compiler_specific.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/threading/thread_checker.h"
 #include "mojo/public/cpp/bindings/bindings_export.h"
 #include "mojo/public/cpp/bindings/message.h"
 #include "mojo/public/cpp/bindings/sync_handle_watcher.h"
 #include "mojo/public/cpp/system/core.h"
 #include "mojo/public/cpp/system/watcher.h"
 
 namespace base {
 class Lock;
@@ skipping 166 matching lines @@
   std::unique_ptr<Watcher> handle_watcher_;
 
   bool error_ = false;
   bool drop_writes_ = false;
   bool enforce_errors_from_incoming_receiver_ = true;
 
   bool paused_ = false;
 
   // If sending messages is allowed from multiple threads, |lock_| is used to
   // protect modifications to |message_pipe_| and |drop_writes_|.
-  std::unique_ptr<base::Lock> lock_;
+  base::Optional<base::Lock> lock_;
 
   std::unique_ptr<SyncHandleWatcher> sync_watcher_;
   bool allow_woken_up_by_others_ = false;
   // If non-zero, currently the control flow is inside the sync handle watcher
   // callback.
   size_t sync_handle_watcher_callback_count_ = 0;
 
   base::ThreadChecker thread_checker_;
 
   base::Lock connected_lock_;
   bool connected_ = true;
 
   // The tag used to track heap allocations that originated from a Watcher
   // notification.
   const char* heap_profiler_tag_ = nullptr;
 
   // Create a single weak ptr and use it everywhere, to avoid the malloc/free
   // cost of creating a new weak ptr whenever it is needed.
   // NOTE: This weak pointer is invalidated when the message pipe is closed or
   // transferred (i.e., when |connected_| is set to false).
   base::WeakPtr<Connector> weak_self_;
   base::WeakPtrFactory<Connector> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Connector);
 };
 
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_CONNECTOR_H_