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

media/cast/sender/audio_sender.cc

Index: media/cast/sender/audio_sender.cc
diff --git a/media/cast/sender/audio_sender.cc b/media/cast/sender/audio_sender.cc
index 1dee7bcb876bc0addf52488d14b723c5839f5cb7..13db1005bfea12aac2240e51e09754e2e0084a86 100644
--- a/media/cast/sender/audio_sender.cc
+++ b/media/cast/sender/audio_sender.cc
@@ -30,8 +30,8 @@ AudioSender::AudioSender(scoped_refptr<CastEnvironment> cast_environment,
     audio_encoder_.reset(new AudioEncoder(
         cast_environment, audio_config.channels, audio_config.rtp_timebase,
         audio_config.max_bitrate, audio_config.codec,
-        base::Bind(&AudioSender::OnEncodedAudioFrame,
-                   weak_factory_.GetWeakPtr(), audio_config.max_bitrate)));
+        base::Bind(&AudioSender::OnEncodedAudioFrame, AsWeakPtr(),
+                   audio_config.max_bitrate)));
   }
 
   // AudioEncoder provides no operational status changes during normal use.
@@ -72,6 +72,10 @@ void AudioSender::InsertAudio(std::unique_ptr<AudioBus> audio_bus,
   audio_encoder_->InsertAudio(std::move(audio_bus), recorded_time);
 }
 
+base::WeakPtr<AudioSender> AudioSender::AsWeakPtr() {
+  return weak_factory_.GetWeakPtr();
+}
+
 int AudioSender::GetNumberOfFramesInEncoder() const {
   // Note: It's possible for a partial frame to be in the encoder, but returning
   // the floor() is good enough for the "design limit" check in FrameSender.