Fix a data race in AudioEncoderMutableImpl and derived classes

webrtc/modules/audio_coding/codecs/opus/interface/audio_encoder_opus.h

 /*
  *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 75 matching lines @@
   bool SetFec(bool enable) override;
 
   // Set Opus DTX. Once enabled, Opus stops transmission, when it detects voice
   // being inactive. During that, it still sends 2 packets (one for content, one
   // for signaling) about every 400 ms.
   bool SetDtx(bool enable) override;
 
   bool SetApplication(Application application) override;
   bool SetMaxPlaybackRate(int frequency_hz) override;
   AudioEncoderOpus::ApplicationMode application() const {
+    CriticalSectionScoped cs(encoder_lock_.get());
     return encoder()->application();
   }
-  double packet_loss_rate() const { return encoder()->packet_loss_rate(); }
-  bool dtx_enabled() const { return encoder()->dtx_enabled(); }
+  double packet_loss_rate() const {
+    CriticalSectionScoped cs(encoder_lock_.get());
+    return encoder()->packet_loss_rate();
+  }
+  bool dtx_enabled() const {
+    CriticalSectionScoped cs(encoder_lock_.get());
+    return encoder()->dtx_enabled();
+  }
 };
 
 }  // namespace webrtc
 #endif  // WEBRTC_MODULES_AUDIO_CODING_CODECS_OPUS_INTERFACE_AUDIO_ENCODER_OPUS_H_