Revert of Avoid calling PostTask in audio callbacks

webrtc/modules/audio_device/audio_device_buffer.h

Index: webrtc/modules/audio_device/audio_device_buffer.h
diff --git a/webrtc/modules/audio_device/audio_device_buffer.h b/webrtc/modules/audio_device/audio_device_buffer.h
index 1466e6934b08303fa4920b3bc54d7bbd21c24b12..e2c6f2871a5fad2f0443ca878c979bddfe2bd899 100644
--- a/webrtc/modules/audio_device/audio_device_buffer.h
+++ b/webrtc/modules/audio_device/audio_device_buffer.h
@@ -12,7 +12,6 @@
 #define WEBRTC_MODULES_AUDIO_DEVICE_AUDIO_DEVICE_BUFFER_H_
 
 #include "webrtc/base/buffer.h"
-#include "webrtc/base/criticalsection.h"
 #include "webrtc/base/task_queue.h"
 #include "webrtc/base/thread_annotations.h"
 #include "webrtc/base/thread_checker.h"
@@ -37,43 +36,6 @@
     LOG_ACTIVE,
   };
 
-  struct Stats {
-    void ResetRecStats() {
-      rec_callbacks = 0;
-      rec_samples = 0;
-      max_rec_level = 0;
-    }
-
-    void ResetPlayStats() {
-      play_callbacks = 0;
-      play_samples = 0;
-      max_play_level = 0;
-    }
-
-    // Total number of recording callbacks where the source provides 10ms audio
-    // data each time.
-    uint64_t rec_callbacks = 0;
-
-    // Total number of playback callbacks where the sink asks for 10ms audio
-    // data each time.
-    uint64_t play_callbacks = 0;
-
-    // Total number of recorded audio samples.
-    uint64_t rec_samples = 0;
-
-    // Total number of played audio samples.
-    uint64_t play_samples = 0;
-
-    // Contains max level (max(abs(x))) of recorded audio packets over the last
-    // 10 seconds where a new measurement is done twice per second. The level
-    // is reset to zero at each call to LogStats().
-    int16_t max_rec_level = 0;
-
-    // Contains max level of recorded audio packets over the last 10 seconds
-    // where a new measurement is done twice per second.
-    int16_t max_play_level = 0;
-  };
-
   AudioDeviceBuffer();
   virtual ~AudioDeviceBuffer();
 
@@ -130,8 +92,9 @@
   // state = LOG_ACTIVE => logs are printed and the timer is kept alive.
   void LogStats(LogState state);
 
-  // Updates counters in each play/record callback. These counters are later
-  // (periodically) read by LogStats() using a lock.
+  // 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(int16_t max_abs, size_t samples_per_channel);
   void UpdatePlayStats(int16_t max_abs, size_t samples_per_channel);
 
@@ -156,8 +119,6 @@
 
   // Native (platform specific) audio thread driving the recording side.
   rtc::ThreadChecker recording_thread_checker_;
-
-  rtc::CriticalSection lock_;
 
   // 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
@@ -223,6 +184,41 @@
   // Counts number of times LogStats() has been called.
   size_t num_stat_reports_ ACCESS_ON(task_queue_);
 
+  // Total number of recording callbacks where the source provides 10ms audio
+  // data each time.
+  uint64_t rec_callbacks_ ACCESS_ON(task_queue_);
+
+  // Total number of recording callbacks stored at the last timer task.
+  uint64_t last_rec_callbacks_ ACCESS_ON(task_queue_);
+
+  // Total number of playback callbacks where the sink asks for 10ms audio
+  // data each time.
+  uint64_t play_callbacks_ ACCESS_ON(task_queue_);
+
+  // Total number of playout callbacks stored at the last timer task.
+  uint64_t last_play_callbacks_ ACCESS_ON(task_queue_);
+
+  // Total number of recorded audio samples.
+  uint64_t rec_samples_ ACCESS_ON(task_queue_);
+
+  // Total number of recorded samples stored at the previous timer task.
+  uint64_t last_rec_samples_ ACCESS_ON(task_queue_);
+
+  // Total number of played audio samples.
+  uint64_t play_samples_ ACCESS_ON(task_queue_);
+
+  // Total number of played samples stored at the previous timer task.
+  uint64_t last_play_samples_ ACCESS_ON(task_queue_);
+
+  // Contains max level (max(abs(x))) of recorded audio packets over the last
+  // 10 seconds where a new measurement is done twice per second. The level
+  // is reset to zero at each call to LogStats().
+  int16_t max_rec_level_ ACCESS_ON(task_queue_);
+
+  // Contains max level of recorded audio packets over the last 10 seconds
+  // where a new measurement is done twice per second.
+  int16_t max_play_level_ ACCESS_ON(task_queue_);
+
   // Time stamp of last timer task (drives logging).
   int64_t last_timer_task_time_ ACCESS_ON(task_queue_);
 
@@ -234,13 +230,6 @@
   // Time stamps of when playout and recording starts.
   int64_t play_start_time_ ACCESS_ON(main_thread_checker_);
   int64_t rec_start_time_ ACCESS_ON(main_thread_checker_);
-
-  // Contains counters for playout and recording statistics.
-  Stats stats_ GUARDED_BY(lock_);
-
-  // Stores current stats at each timer task. Used to calculate differences
-  // between two successive timer events.
-  Stats last_stats_ ACCESS_ON(task_queue_);
 
   // Set to true at construction and modified to false as soon as one audio-
   // level estimate larger than zero is detected.