Notify NetEqController during muted state.

During muted state NetEq shortcircuits a large part of the internals to
quickly return a buffer filled with zeros. It can be beneficial for the
controller to be aware that it is in muted state.

Bug: webrtc:11005
Change-Id: I5fe24b4a3704d953cbd68b5a24bbb7ef58b30be0
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/186760
Commit-Queue: Ivo Creusen <ivoc@webrtc.org>
Reviewed-by: Jakob Ivarsson <jakobi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32330}

modules/audio_coding/neteq/decision_logic.h

@@ -84,6 +84,8 @@ class DecisionLogic : public NetEqController {
 
   void RegisterEmptyPacket() override { delay_manager_->RegisterEmptyPacket(); }
 
+  void NotifyMutedState() override {}
+
   bool SetMaximumDelay(int delay_ms) override {
     return delay_manager_->SetMaximumDelay(delay_ms);
   }