Introduce struct MediaConfig, with construction-time settings.

talk/app/webrtc/peerconnection.cc

 /*
  * libjingle
  * Copyright 2012 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  *  1. Redistributions of source code must retain the above copyright notice,
  *     this list of conditions and the following disclaimer.
  *  2. Redistributions in binary form must reproduce the above copyright notice,
@@ skipping 615 matching lines @@
 
   if (configuration.tcp_candidate_policy == kTcpCandidatePolicyDisabled) {
     portallocator_flags |= cricket::PORTALLOCATOR_DISABLE_TCP;
     LOG(LS_INFO) << "TCP candidates are disabled.";
   }
 
   port_allocator_->set_flags(portallocator_flags);
   // No step delay is used while allocating ports.
   port_allocator_->set_step_delay(cricket::kMinimumStepDelay);
 
-  media_controller_.reset(factory_->CreateMediaController());
+  // We rely on default values when constraints aren't found.
+  MediaConfig media_config;
+
+  media_config.disable_prerenderer_smoothing =
+    configuration.disable_prerenderer_smoothing;
+
+  // Find DSCP constraint.
+  FindConstraint(constraints,
+                 MediaConstraintsInterface::kEnableDscp,
+                 &media_config.enable_dscp, NULL);
+  // Find constraints for cpu overuse detection.
+  FindConstraint(constraints,
+                 MediaConstraintsInterface::kCpuOveruseDetection,
+                 &media_config.cpu_overuse_detection, NULL);
+
+  media_controller_.reset(factory_->CreateMediaController(media_config));
 
   remote_stream_factory_.reset(new RemoteMediaStreamFactory(
       factory_->signaling_thread(), media_controller_->channel_manager()));
 
   session_.reset(
       new WebRtcSession(media_controller_.get(), factory_->signaling_thread(),
                         factory_->worker_thread(), port_allocator_.get()));
   stats_.reset(new StatsCollector(this));
 
   // Initialize the WebRtcSession. It creates transport channels etc.
@@ skipping 1441 matching lines @@
 DataChannel* PeerConnection::FindDataChannelBySid(int sid) const {
   for (const auto& channel : sctp_data_channels_) {
     if (channel->id() == sid) {
       return channel;
     }
   }
   return nullptr;
 }
 
 }  // namespace webrtc