Call ChannelManager aec dump methods on the worker thread.

Before, the calls went through the signaling thread and
blocked while the operation completed on the worker.

Bug: webrtc:12601
Change-Id: I58991fa98a55d0fa9304a68bd85bb269f1f123d2
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/212619
Commit-Queue: Tommi <tommi@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33615}
diff --git a/pc/peer_connection_factory.h b/pc/peer_connection_factory.h
index cbc7397..71d7830 100644
--- a/pc/peer_connection_factory.h
+++ b/pc/peer_connection_factory.h
@@ -117,6 +117,8 @@
     return context_->signaling_thread();
   }
 
+  rtc::Thread* worker_thread() const { return context_->worker_thread(); }
+
   const Options& options() const {
     RTC_DCHECK_RUN_ON(signaling_thread());
     return options_;
@@ -137,7 +139,6 @@
   virtual ~PeerConnectionFactory();
 
  private:
-  rtc::Thread* worker_thread() const { return context_->worker_thread(); }
   rtc::Thread* network_thread() const { return context_->network_thread(); }
 
   bool IsTrialEnabled(absl::string_view key) const;