Add health checker for CMA mixer thread

Mixer thread somehow gets stuck forever, not able to recover.
Using ThreadHealthChecker to workaround

Bug: b/136353019
Test: build & run
Change-Id: Ifbc0bd1bca1da88124e5fc326e8db296f825a6d1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1697317Reviewed-by: Kenneth MacKay <kmackay@chromium.org>
Commit-Queue: Yi Fan <yfa@chromium.org>
Cr-Commit-Position: refs/heads/master@{#676548}

chromecast/media/cma/backend/BUILD.gn

@@ -258,6 +258,7 @@ cast_source_set("for_mixer_audio") {
     ":volume_map",
     "//base",
     "//chromecast/base",
+    "//chromecast/base:thread_health_checker",
     "//chromecast/media/audio:libcast_external_audio_pipeline_1.0",
     "//chromecast/media/base",
     "//chromecast/media/cma/base",

chromecast/media/cma/backend/stream_mixer.cc

@@ -22,6 +22,7 @@
 #include "build/build_config.h"
 #include "chromecast/base/chromecast_switches.h"
 #include "chromecast/base/serializers.h"
+#include "chromecast/base/thread_health_checker.h"
 #include "chromecast/media/base/audio_device_ids.h"
 #include "chromecast/media/cma/backend/audio_output_redirector.h"
 #include "chromecast/media/cma/backend/cast_audio_json.h"
@@ -56,6 +57,11 @@
 namespace chromecast {
 namespace media {
 
+constexpr base::TimeDelta kMixerThreadCheckTimeout =
+    base::TimeDelta::FromSeconds(10);
+constexpr base::TimeDelta kHealthCheckInterval =
+    base::TimeDelta::FromSeconds(5);
+
 class StreamMixer::ExternalLoopbackAudioObserver
     : public CastMediaShlib::LoopbackAudioObserver {
  public:
@@ -221,6 +227,13 @@ StreamMixer::StreamMixer(
     loopback_options.priority = base::ThreadPriority::REALTIME_AUDIO;
     loopback_thread_->StartWithOptions(loopback_options);
     loopback_task_runner_ = loopback_thread_->task_runner();
+
+    health_checker_ = std::make_unique<ThreadHealthChecker>(
+        mixer_task_runner_, loopback_task_runner_, kHealthCheckInterval,
+        kMixerThreadCheckTimeout,
+        base::BindRepeating(&StreamMixer::OnHealthCheckFailed,
+                            base::Unretained(this)));
+    LOG(INFO) << "Mixer health checker started";
   } else {
     loopback_task_runner_ = mixer_task_runner_;
   }
@@ -249,6 +262,10 @@ StreamMixer::StreamMixer(
   }
 }
 
+void StreamMixer::OnHealthCheckFailed() {
+  LOG(FATAL) << "Crash on mixer thread health check failure!";
+}
+
 void StreamMixer::ResetPostProcessors(CastMediaShlib::ResultCallback callback) {
   RUN_ON_MIXER_THREAD(ResetPostProcessorsOnThread, std::move(callback), "");
 }

chromecast/media/cma/backend/stream_mixer.h

@@ -28,6 +28,8 @@
 #include "chromecast/public/volume_control.h"
 
 namespace chromecast {
+class ThreadHealthChecker;
+
 namespace media {
 
 class AudioOutputRedirector;
@@ -195,6 +197,9 @@ class StreamMixer {
   scoped_refptr<base::SingleThreadTaskRunner> mixer_task_runner_;
   std::unique_ptr<base::Thread> loopback_thread_;
   scoped_refptr<base::SingleThreadTaskRunner> loopback_task_runner_;
+  std::unique_ptr<ThreadHealthChecker> health_checker_;
+
+  void OnHealthCheckFailed();
 
   int num_output_channels_;
   const int low_sample_rate_cutoff_;