Make MediaSession a runtime-enabled feature on Desktop.

media/base/media_switches.cc

 // 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.
 
 #include "build/build_config.h"
 #include "media/base/media_switches.h"
 
 namespace switches {
 
 // Allow users to specify a custom buffer size for debugging purpose.
@@ skipping 79 matching lines @@
 
 // Number of buffers to use for WaveOut.
 const char kWaveOutBuffers[] = "waveout-buffers";
 #endif
 
 #if defined(USE_CRAS)
 // Use CRAS, the ChromeOS audio server.
 const char kUseCras[] = "use-cras";
 #endif
 
+#if !defined(OS_ANDROID)
+// Use a media session for each tabs in a way that two tabs can't play on top of
+// each other. This is different from the Media Session API as it is enabling a
+// default behaviour for the browser.
+const char kEnableDefaultMediaSession[] = "enable-default-media-session";
+#endif
+
 // Use fake device for Media Stream to replace actual camera and microphone.
 const char kUseFakeDeviceForMediaStream[] = "use-fake-device-for-media-stream";
 
 // Use an .y4m file to play as the webcam. See the comments in
 // media/capture/video/file_video_capture_device.h for more details.
 const char kUseFileForFakeVideoCapture[] = "use-file-for-fake-video-capture";
 
 // Play a .wav file as the microphone. Note that for WebRTC calls we'll treat
 // the bits as if they came from the microphone, which means you should disable
 // audio processing (lest your audio file will play back distorted). The input
@@ skipping 21 matching lines @@
 
 }  // namespace switches
 
 namespace media {
 
 // Use shared block-based buffering for media.
 const base::Feature kUseNewMediaCache{"use-new-media-cache",
                                       base::FEATURE_DISABLED_BY_DEFAULT};
 
 }  // namespace media