Reland of Adds data logging in native AudioDeviceBuffer class (patchset #1 id:1 of https://codereview.webrtc.org/2139233002/ )

Reason for revert:
My original patch broke things that are now fixed by https://codereview.webrtc.org/2141193002/.

Hence I am relanding my original change.

Original issue's description:
> Revert of Adds data logging in native AudioDeviceBuffer class (patchset #10 id:180001 of https://codereview.webrtc.org/2132613002/ )
>
> Reason for revert:
> Seems to break things upstream.
>
> Original issue's description:
> > Adds data logging in native AudioDeviceBuffer class.
> >
> > Goal is to provide periodic logging of most essential audio parameters
> > for playout and recording sides. It will allow us to track if the native audio layer is working as intended.
> >
> > BUG=NONE
> >
> > Committed: https://crrev.com/348e411dd27e6dbe9b84b27ce46e9b7c657c1eae
> > Cr-Commit-Position: refs/heads/master@{#13440}
>
> TBR=stefan@webrtc.org,henrika@webrtc.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=NONE
>
> Committed: https://crrev.com/025aa94ccb85e4c6fe20a3fecdac5d27ec9ba3da
> Cr-Commit-Position: refs/heads/master@{#13441}

TBR=stefan@webrtc.org,sprang@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=NONE

Review-Url: https://codereview.webrtc.org/2138403003
Cr-Commit-Position: refs/heads/master@{#13455}

webrtc/modules/audio_device/audio_device_buffer.h

@@ -8,9 +8,12 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#ifndef WEBRTC_AUDIO_DEVICE_AUDIO_DEVICE_BUFFER_H
-#define WEBRTC_AUDIO_DEVICE_AUDIO_DEVICE_BUFFER_H
+#ifndef WEBRTC_MODULES_AUDIO_DEVICE_AUDIO_DEVICE_BUFFER_H_
+#define WEBRTC_MODULES_AUDIO_DEVICE_AUDIO_DEVICE_BUFFER_H_
 
+#include "webrtc/base/criticalsection.h"
+#include "webrtc/base/task_queue.h"
+#include "webrtc/base/thread_checker.h"
 #include "webrtc/modules/audio_device/include/audio_device.h"
 #include "webrtc/system_wrappers/include/file_wrapper.h"
 #include "webrtc/typedefs.h"
@@ -63,11 +66,36 @@ class AudioDeviceBuffer {
   int32_t SetTypingStatus(bool typingStatus);
 
  private:
-  CriticalSectionWrapper& _critSect;
-  CriticalSectionWrapper& _critSectCb;
+  // Posts the first delayed task in the task queue and starts the periodic
+  // timer.
+  void StartTimer();
+
+  // Called periodically on the internal thread created by the TaskQueue.
+  void LogStats();
+
+  // Updates counters in each play/record callback but does it on the task
+  // queue to ensure that they can be read by LogStats() without any locks since
+  // each task is serialized by the task queue.
+  void UpdateRecStats(size_t num_samples);
+  void UpdatePlayStats(size_t num_samples);
+
+  // Ensures that methods are called on the same thread as the thread that
+  // creates this object.
+  rtc::ThreadChecker thread_checker_;
+
+  rtc::CriticalSection _critSect;
+  rtc::CriticalSection _critSectCb;
 
   AudioTransport* _ptrCbAudioTransport;
 
+  // Task queue used to invoke LogStats() periodically. Tasks are executed on a
+  // worker thread but it does not necessarily have to be the same thread for
+  // each task.
+  rtc::TaskQueue task_queue_;
+
+  // Ensures that the timer is only started once.
+  bool timer_has_started_;
+
   uint32_t _recSampleRate;
   uint32_t _playSampleRate;
 
@@ -107,8 +135,40 @@ class AudioDeviceBuffer {
   int _recDelayMS;
   int _clockDrift;
   int high_delay_counter_;
+
+  // Counts number of times LogStats() has been called.
+  size_t num_stat_reports_;
+
+  // Total number of recording callbacks where the source provides 10ms audio
+  // data each time.
+  uint64_t rec_callbacks_;
+
+  // Total number of recording callbacks stored at the last timer task.
+  uint64_t last_rec_callbacks_;
+
+  // Total number of playback callbacks where the sink asks for 10ms audio
+  // data each time.
+  uint64_t play_callbacks_;
+
+  // Total number of playout callbacks stored at the last timer task.
+  uint64_t last_play_callbacks_;
+
+  // Total number of recorded audio samples.
+  uint64_t rec_samples_;
+
+  // Total number of recorded samples stored at the previous timer task.
+  uint64_t last_rec_samples_;
+
+  // Total number of played audio samples.
+  uint64_t play_samples_;
+
+  // Total number of played samples stored at the previous timer task.
+  uint64_t last_play_samples_;
+
+  // Time stamp of last stat report.
+  uint64_t last_log_stat_time_;
 };
 
 }  // namespace webrtc
 
-#endif  // WEBRTC_AUDIO_DEVICE_AUDIO_DEVICE_BUFFER_H
+#endif  // WEBRTC_MODULES_AUDIO_DEVICE_AUDIO_DEVICE_BUFFER_H_