Fix threading issues in the audio pipeline for WebRTC remoting protocol.

remoting/protocol/webrtc_audio_module.h

Index: remoting/protocol/webrtc_audio_module.h
diff --git a/remoting/protocol/webrtc_audio_module.h b/remoting/protocol/webrtc_audio_module.h
index 19f6e5422d49cc53baa1c6fe24ef34d8731296a1..82a0d398dbbb5635f77e76eb91f7dae81c9ae38f 100644
--- a/remoting/protocol/webrtc_audio_module.h
+++ b/remoting/protocol/webrtc_audio_module.h
@@ -7,10 +7,10 @@
 
 #include "base/memory/ref_counted.h"
 #include "base/synchronization/lock.h"
-#include "base/timer/timer.h"
 #include "third_party/webrtc/modules/audio_device/include/audio_device.h"
 
 namespace base {
+class RepeatingTimer;
 class SingleThreadTaskRunner;
 }  // namespace base
 
@@ -155,7 +155,7 @@ class WebrtcAudioModule : public webrtc::AudioDeviceModule {
 
   // Timer running on the |audio_task_runner_| that polls audio from
   // |audio_transport_|.
-  base::RepeatingTimer poll_timer_;
+  std::unique_ptr<base::RepeatingTimer> poll_timer_;
 };
 
 }  // namespace protocol