Web MIDI: add dynamic MidiManager instantiation support for Linux

media/midi/midi_manager_usb_unittest.cc

 // Copyright 2014 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.
 
 #include "media/midi/midi_manager_usb.h"
 
 #include <stddef.h>
 #include <stdint.h>
 #include <memory>
 #include <string>
@@ skipping 152 matching lines @@
   Callback callback_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(TestUsbMidiDeviceFactory);
 };
 
 class MidiManagerUsbForTesting : public MidiManagerUsb {
  public:
   explicit MidiManagerUsbForTesting(
       std::unique_ptr<UsbMidiDevice::Factory> device_factory)
-      : MidiManagerUsb(std::move(device_factory)) {}
+      : MidiManagerUsb(nullptr, std::move(device_factory)) {}
   ~MidiManagerUsbForTesting() override {}
 
   void CallCompleteInitialization(Result result) {
     CompleteInitialization(result);
     base::RunLoop run_loop;
     run_loop.RunUntilIdle();
   }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(MidiManagerUsbForTesting);
@@ skipping 385 matching lines @@
   EXPECT_EQ(2u, manager_->output_streams()[0]->jack().jack_id);
   EXPECT_EQ(3u, manager_->output_streams()[1]->jack().jack_id);
   ASSERT_EQ(1u, jacks.size());
   EXPECT_EQ(2, jacks[0].endpoint_number());
   EXPECT_EQ("UsbMidiDevice::GetDescriptors\n", logger_.TakeLog());
 }
 
 }  // namespace
 
 }  // namespace midi