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/interface/video_coding.h

@@ -82,9 +82,7 @@ public:
     };
 
     static VideoCodingModule* Create(
-        Clock* clock,
-        VideoEncoderRateObserver* encoder_rate_observer,
-        VCMQMSettingsCallback* qm_settings_callback);
+        VideoEncoderRateObserver* encoder_rate_observer);
 
     static VideoCodingModule* Create(Clock* clock, EventFactory* event_factory);
 
@@ -269,6 +267,16 @@ public:
     virtual int32_t RegisterSendStatisticsCallback(
                                      VCMSendStatisticsCallback* sendStats) = 0;
 
+    // Register a video quality settings callback which will be called when
+    // frame rate/dimensions need to be updated for video quality optimization
+    //
+    // Input:
+    //      - videoQMSettings  : The callback object to register.
+    //
+    // Return value      : VCM_OK, on success.
+    //                     < 0,         on error
+    virtual int32_t RegisterVideoQMCallback(VCMQMSettingsCallback* videoQMSettings) = 0;
+
     // Register a video protection callback which will be called to deliver
     // the requested FEC rate and NACK status (on/off).
     //