MidiScheduler binds to task runner of constructing thread

media/midi/midi_manager_android.h

Index: media/midi/midi_manager_android.h
diff --git a/media/midi/midi_manager_android.h b/media/midi/midi_manager_android.h
index 4269d5d8526d943b98a03d8ff7b4e3aac0bd56fb..8da77510c9a45d6d0fdae1baaad2667f5460b38d 100644
--- a/media/midi/midi_manager_android.h
+++ b/media/midi/midi_manager_android.h
@@ -15,6 +15,7 @@
 #include "base/android/scoped_java_ref.h"
 #include "base/containers/hash_tables.h"
 #include "base/memory/scoped_vector.h"
+#include "base/synchronization/lock.h"
 #include "base/time/time.h"
 #include "media/midi/midi_input_port_android.h"
 #include "media/midi/midi_manager.h"
@@ -36,6 +37,7 @@ class MidiManagerAndroid final : public MidiManager,
 
   // MidiManager implementation.
   void StartInitialization() override;
+  void Finalize() override;
   void DispatchSendMidiData(MidiManagerClient* client,
                             uint32_t port_index,
                             const std::vector<uint8_t>& data,
@@ -81,7 +83,11 @@ class MidiManagerAndroid final : public MidiManager,
   base::hash_map<MidiOutputPortAndroid*, size_t> output_port_to_index_;
 
   base::android::ScopedJavaGlobalRef<jobject> raw_manager_;
-  std::unique_ptr<MidiScheduler> scheduler_;
+
+  // Lock to ensure the MidiScheduler is being destructed only once in
+  // Finalize() on Chrome_IOThread.
+  base::Lock scheduler_lock_;
+  std::unique_ptr<MidiScheduler> scheduler_;  // GUARDED_BY(scheduler_lock_)
 };
 
 }  // namespace midi