Enable WebMIDI for Windows behind the flag

media/midi/midi_manager.cc

 // Copyright (c) 2013 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.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/message_loop/message_loop.h"
 #include "base/threading/thread.h"
 
 namespace media {
 
-#if !defined(OS_MACOSX)
+#if !defined(OS_MACOSX) &&  !defined(OS_WIN)
 // TODO(crogers): implement MIDIManager for other platforms.
 MIDIManager* MIDIManager::Create() {
   return NULL;
 }
 #endif
 
 MIDIManager::MIDIManager()
     : initialized_(false) {
 }
 
@@ skipping 53 matching lines @@
     send_message_loop_ = send_thread_->message_loop_proxy();
   }
 
   send_message_loop_->PostTask(
      FROM_HERE,
      base::Bind(&MIDIManager::SendMIDIData, base::Unretained(this),
          client, port_index, data, timestamp));
 }
 
 }  // namespace media