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

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

Index: mojo/public/cpp/bindings/lib/may_auto_lock.h
diff --git a/mojo/public/cpp/bindings/lib/may_auto_lock.h b/mojo/public/cpp/bindings/lib/may_auto_lock.h
index 42bbfae5d64ef0e10c771c598b6db819e0932f53..06091fee90c91dcc8ee7896aa362e69c67acc917 100644
--- a/mojo/public/cpp/bindings/lib/may_auto_lock.h
+++ b/mojo/public/cpp/bindings/lib/may_auto_lock.h
@@ -6,6 +6,7 @@
 #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 {
@@ -15,7 +16,8 @@ namespace internal {
 // 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();
   }
@@ -36,7 +38,8 @@ class MayAutoLock {
 // 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();