Web MIDI: add dynamic MidiManager instantiation support for Linux

media/midi/midi_manager_usb.cc

Index: media/midi/midi_manager_usb.cc
diff --git a/media/midi/midi_manager_usb.cc b/media/midi/midi_manager_usb.cc
index 70b2fa9765cd87e77162bc3a597d46890adb22e9..56e08c8d52ba0beb3c06e9299c70bb9b09e69731 100644
--- a/media/midi/midi_manager_usb.cc
+++ b/media/midi/midi_manager_usb.cc
@@ -17,8 +17,9 @@ namespace midi {
 using mojom::PortState;
 using mojom::Result;
 
-MidiManagerUsb::MidiManagerUsb(std::unique_ptr<UsbMidiDevice::Factory> factory)
-    : device_factory_(std::move(factory)) {}
+MidiManagerUsb::MidiManagerUsb(MidiService* service,
+                               std::unique_ptr<UsbMidiDevice::Factory> factory)
+    : MidiManager(service), device_factory_(std::move(factory)) {}
 
 MidiManagerUsb::~MidiManagerUsb() {
   base::AutoLock auto_lock(scheduler_lock_);