Reland: Web MIDI: split build rules for media/midi

media/midi/midi_scheduler.h

Index: media/midi/midi_scheduler.h
diff --git a/media/midi/midi_scheduler.h b/media/midi/midi_scheduler.h
index 73c8bc61f653f0ce3f2809b492960eae1fcfbc67..452328b064a735bb95f732522db21e59f57ad532 100644
--- a/media/midi/midi_scheduler.h
+++ b/media/midi/midi_scheduler.h
@@ -7,6 +7,7 @@
 
 #include "base/callback.h"
 #include "base/memory/weak_ptr.h"
+#include "media/base/media_export.h"
 
 namespace media {
 
@@ -14,7 +15,7 @@ class MidiManager;
 class MidiManagerClient;
 
 // TODO(crbug.com/467442): Make tasks cancelable per client.
-class MidiScheduler final {
+class MEDIA_EXPORT MidiScheduler final {
  public:
   explicit MidiScheduler(MidiManager* manager);
   ~MidiScheduler();