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..bfa52caf1d4198801c761421e9a31d23d5fd88b4 100644
--- a/media/cast/sender/audio_sender.cc
+++ b/media/cast/sender/audio_sender.cc
@@ -24,14 +24,13 @@ AudioSender::AudioSender(scoped_refptr<CastEnvironment> cast_environment,
                   transport_sender,
                   audio_config,
                   NewFixedCongestionControl(audio_config.max_bitrate)),
-      samples_in_encoder_(0),
-      weak_factory_(this) {
+      samples_in_encoder_(0) {
   if (!audio_config.use_external_encoder) {
     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.