Remove base::SupportsWeakPtr from {Audio,Video}Sender

media/cast/sender/audio_sender.h

Index: media/cast/sender/audio_sender.h
diff --git a/media/cast/sender/audio_sender.h b/media/cast/sender/audio_sender.h
index 17fda1f7af1651f7996bcb819380c43c7dbb6522..315f5f8c554549355b58b91420f41a4ca1ed3377 100644
--- a/media/cast/sender/audio_sender.h
+++ b/media/cast/sender/audio_sender.h
@@ -30,9 +30,7 @@ class AudioEncoder;
 // RTCP packets.
 // Additionally it posts a bunch of delayed tasks to the main thread for various
 // timeouts.
-class AudioSender : public FrameSender,
-                    public base::NonThreadSafe,
-                    public base::SupportsWeakPtr<AudioSender> {
+class AudioSender : public FrameSender, public base::NonThreadSafe {
  public:
   AudioSender(scoped_refptr<CastEnvironment> cast_environment,
               const FrameSenderConfig& audio_config,
@@ -47,6 +45,8 @@ class AudioSender : public FrameSender,
   void InsertAudio(std::unique_ptr<AudioBus> audio_bus,
                    const base::TimeTicks& recorded_time);
 
+  base::WeakPtr<AudioSender> AsWeakPtr();
+
  protected:
   int GetNumberOfFramesInEncoder() const final;
   base::TimeDelta GetInFlightMediaDuration() const final;