Work-in-progress upload to add worker task queue to PC factory.

webrtc/media/base/mediaengine.h

Index: webrtc/media/base/mediaengine.h
diff --git a/webrtc/media/base/mediaengine.h b/webrtc/media/base/mediaengine.h
index 2b9e790a6c09d4b27139d31b66d78a63bdd2cf36..872cd0e3b55212d268b0fbfb7720e0f601585d56 100644
--- a/webrtc/media/base/mediaengine.h
+++ b/webrtc/media/base/mediaengine.h
@@ -23,6 +23,7 @@
 #include "webrtc/api/rtpparameters.h"
 #include "webrtc/base/fileutils.h"
 #include "webrtc/base/sigslotrepeater.h"
+#include "webrtc/base/task_queue.h"
 #include "webrtc/call/audio_state.h"
 #include "webrtc/media/base/codec.h"
 #include "webrtc/media/base/mediachannel.h"
@@ -32,6 +33,10 @@
 #define DISABLE_MEDIA_ENGINE_FACTORY
 #endif
 
+namespace rtc {
+class TaskQueue;
+}
+
 namespace webrtc {
 class AudioDeviceModule;
 class AudioMixer;
@@ -117,9 +122,20 @@ class CompositeMediaEngine : public MediaEngineInterface {
                            audio_encoder_factory,
                        const rtc::scoped_refptr<webrtc::AudioDecoderFactory>&
                            audio_decoder_factory,
-                       rtc::scoped_refptr<webrtc::AudioMixer> audio_mixer)
-      : voice_(adm, audio_encoder_factory, audio_decoder_factory, audio_mixer) {
-  }
+                       rtc::scoped_refptr<webrtc::AudioMixer> audio_mixer,
+                       rtc::TaskQueue* low_priority_worker_queue)
+      : owned_low_priority_worker_queue_(
+            low_priority_worker_queue
+                ? nullptr
+                : new rtc::TaskQueue("low_prio_worker_queue",
+                                     rtc::TaskQueue::Priority::LOW)),
+        voice_(adm,
+               audio_encoder_factory,
+               audio_decoder_factory,
+               audio_mixer,
+               low_priority_worker_queue
+                   ? owned_low_priority_worker_queue_.get()
+                   : low_priority_worker_queue) {}
   virtual ~CompositeMediaEngine() {}
   virtual bool Init() {
     video_.Init();
@@ -165,6 +181,9 @@ class CompositeMediaEngine : public MediaEngineInterface {
     voice_.StopAecDump();
   }
 
+ private:
+  std::unique_ptr<rtc::TaskQueue> owned_low_priority_worker_queue_;
+
  protected:
   VOICE voice_;
   VIDEO video_;