Revert "Avoid critsect for protection- and qm setting callbacks in VideoSender."

This reverts commit 903c0f2e7649a2b98659286dc228447facd49bb7,
aka #8899.

TBR=pbos@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/46759004

Cr-Commit-Position: refs/heads/master@{#8901}

webrtc/modules/video_coding/main/source/media_optimization.cc

@@ -246,7 +246,7 @@ uint32_t MediaOptimization::SetTargetRates(
 
   // Update protection settings, when applicable.
   float sent_video_rate_kbps = 0.0f;
-  if (loss_prot_logic_->SelectedType() != kNone) {
+  if (selected_method) {
     // Update protection method with content metrics.
     selected_method->UpdateContentMetrics(content_->ShortTermAvgData());