Web MIDI: add dynamic MidiManager instantiation support for Linux

media/midi/midi_manager_winrt.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_MIDI_MIDI_MANAGER_WINRT_H_
 #define MEDIA_MIDI_MIDI_MANAGER_WINRT_H_
 
 #include <memory>
 
 #include "base/strings/string16.h"
 #include "base/threading/thread.h"
 #include "media/midi/midi_manager.h"
 
 namespace base {
 class ThreadChecker;
 }
 
 namespace midi {
 
 class MidiScheduler;
+class MidiService;
 
 class MIDI_EXPORT MidiManagerWinrt final : public MidiManager {
  public:
-  MidiManagerWinrt();
+  explicit MidiManagerWinrt(MidiService* service);
   ~MidiManagerWinrt() override;
 
   // MidiManager overrides:
   void StartInitialization() final;
   void Finalize() final;
   void DispatchSendMidiData(MidiManagerClient* client,
                             uint32_t port_index,
                             const std::vector<uint8_t>& data,
                             double timestamp) final;
 
@@ skipping 41 matching lines @@
 
   // Incremented when a MidiPortManager is ready.
   uint8_t port_manager_ready_count_ = 0;
 
   DISALLOW_COPY_AND_ASSIGN(MidiManagerWinrt);
 };
 
 }  // namespace midi
 
 #endif  // MEDIA_MIDI_MIDI_MANAGER_WINRT_H_