Add about_flag for experimenting MediaSession on Desktop

media/base/media_switches.h

 // Copyright (c) 2012 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.
 
 // Defines all the "media" command-line switches.
 
 #ifndef MEDIA_BASE_MEDIA_SWITCHES_H_
 #define MEDIA_BASE_MEDIA_SWITCHES_H_
 
 #include "base/feature_list.h"
@@ skipping 27 matching lines @@
 MEDIA_EXPORT extern const char kTrySupportedChannelLayouts[];
 MEDIA_EXPORT extern const char kWaveOutBuffers[];
 #endif
 
 #if defined(USE_CRAS)
 MEDIA_EXPORT extern const char kUseCras[];
 #endif
 
 #if !defined(OS_ANDROID)
 MEDIA_EXPORT extern const char kEnableDefaultMediaSession[];
-#endif
+
+#if defined(ENABLE_PLUGINS)
+MEDIA_EXPORT extern const char kEnableDefaultMediaSessionWithFlash[];
+#endif  // defined(ENABLE_PLUGINS)
+
+#endif  // !defined(OS_ANDROID)
 
 MEDIA_EXPORT extern const char kUseFakeDeviceForMediaStream[];
 MEDIA_EXPORT extern const char kUseFileForFakeVideoCapture[];
 MEDIA_EXPORT extern const char kUseFileForFakeAudioCapture[];
 
 MEDIA_EXPORT extern const char kEnableInbandTextTracks[];
 
 MEDIA_EXPORT extern const char kRequireAudioHardwareForTesting[];
 
 MEDIA_EXPORT extern const char kVideoUnderflowThresholdMs[];
@@ skipping 28 matching lines @@
 MEDIA_EXPORT extern const base::Feature kUseNewMediaCache;
 MEDIA_EXPORT extern const base::Feature kVideoColorManagement;
 MEDIA_EXPORT extern const base::Feature kExternalClearKeyForTesting;
 
 #if defined(OS_ANDROID)
 MEDIA_EXPORT extern const base::Feature kAndroidMediaPlayerRenderer;
 #endif  // defined(OS_ANDROID)
 }  // namespace media
 
 #endif  // MEDIA_BASE_MEDIA_SWITCHES_H_