Web MIDI: introduce pending client count limit to start sessions

media/midi/midi_manager.h

Index: media/midi/midi_manager.h
diff --git a/media/midi/midi_manager.h b/media/midi/midi_manager.h
index 156a2465cb424bb943a271fdd4b7f99c53a669f5..6faf80902c3b9f81898e75673b7274c02929840f 100644
--- a/media/midi/midi_manager.h
+++ b/media/midi/midi_manager.h
@@ -50,11 +50,13 @@ class MEDIA_EXPORT MidiManagerClient {
 // Manages access to all MIDI hardware.
 class MEDIA_EXPORT MidiManager {
  public:
-  static MidiManager* Create();
+  static const size_t kMaxPendingClientCount = 128;
 
   MidiManager();
   virtual ~MidiManager();
 
+  static MidiManager* Create();
+
   // A client calls StartSession() to receive and send MIDI data.
   // If the session is ready to start, the MIDI system is lazily initialized
   // and the client is registered to receive MIDI data.