GN Windows component build fixes

media/midi/usb_midi_export.h

+// Copyright 2015 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_USB_MIDI_EXPORT_H_
+#define MEDIA_MIDI_USB_MIDI_EXPORT_H_
+
+// These files can be included as part of the midi component using the

[scottmg, 2015/05/05 01:46:46]

Bleh :(

+// MIDI_IMPLEMENTATION define (where we want to export in the component build),
+// or in the unit tests (where we never want to export/import, even in
+// component mode). The EXPORT_USB_MIDI define controls this.
+#if defined(COMPONENT_BUILD) && defined(EXPORT_USB_MIDI)
+#if defined(WIN32)
+
+#if defined(MIDI_IMPLEMENTATION)
+#define USB_MIDI_EXPORT __declspec(dllexport)
+#else
+#define USB_MIDI_EXPORT __declspec(dllimport)
+#endif  // defined(MIDI_IMPLEMENTATION)
+
+#else  // defined(WIN32)
+#if defined(MIDI_IMPLEMENTATION)
+#define USB_MIDI_EXPORT __attribute__((visibility("default")))
+#else
+#define USB_MIDI_EXPORT
+#endif
+#endif
+
+#else  // defined(COMPONENT_BUILD)
+#define USB_MIDI_EXPORT
+#endif
+
+#endif  // MEDIA_MIDI_USB_MIDI_EXPORT_H_