Require udev for MidiManagerAlsa

media/midi/midi_manager_alsa.h

Index: media/midi/midi_manager_alsa.h
diff --git a/media/midi/midi_manager_alsa.h b/media/midi/midi_manager_alsa.h
index a041004dcd8a2bf7579e5fde6cd558f1448c14b6..200c4c0fac1e57a7a33db12a4092d335f99f5573 100644
--- a/media/midi/midi_manager_alsa.h
+++ b/media/midi/midi_manager_alsa.h
@@ -17,6 +17,7 @@
 #include "base/synchronization/lock.h"
 #include "base/threading/thread.h"
 #include "base/values.h"
+#include "device/udev_linux/scoped_udev.h"
 #include "media/midi/midi_manager.h"
 
 namespace media {
@@ -312,6 +313,9 @@ class MEDIA_EXPORT MidiManagerAlsa final : public MidiManager {
   // ALSA event -> MIDI coder.
   snd_midi_event_t* decoder_;
 
+  // udev, for querying hardware devices.
+  device::ScopedUdevPtr udev_;
+
   base::Thread send_thread_;
   base::Thread event_thread_;