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

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

 // 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.
 
 #ifndef MOJO_PUBLIC_CPP_BINDINGS_LIB_MAY_AUTO_LOCK_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_LIB_MAY_AUTO_LOCK_H_
 
 #include "base/macros.h"
+#include "base/optional.h"
 #include "base/synchronization/lock.h"
 
 namespace mojo {
 namespace internal {
 
 // Similar to base::AutoLock, except that it does nothing if |lock| passed into
 // the constructor is null.
 class MayAutoLock {
  public:
-  explicit MayAutoLock(base::Lock* lock) : lock_(lock) {
+  explicit MayAutoLock(base::Optional<base::Lock>* lock)
+      : lock_(lock->has_value() ? &lock->value() : nullptr) {
     if (lock_)
       lock_->Acquire();
   }
 
   ~MayAutoLock() {
     if (lock_) {
       lock_->AssertAcquired();
       lock_->Release();
     }
   }
 
  private:
   base::Lock* lock_;
   DISALLOW_COPY_AND_ASSIGN(MayAutoLock);
 };
 
 // Similar to base::AutoUnlock, except that it does nothing if |lock| passed
 // into the constructor is null.
 class MayAutoUnlock {
  public:
-  explicit MayAutoUnlock(base::Lock* lock) : lock_(lock) {
+  explicit MayAutoUnlock(base::Optional<base::Lock>* lock)
+      : lock_(lock->has_value() ? &lock->value() : nullptr) {
     if (lock_) {
       lock_->AssertAcquired();
       lock_->Release();
     }
   }
 
   ~MayAutoUnlock() {
     if (lock_)
       lock_->Acquire();
   }
 
  private:
   base::Lock* lock_;
   DISALLOW_COPY_AND_ASSIGN(MayAutoUnlock);
 };
 
 }  // namespace internal
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_MAY_AUTO_LOCK_H_