Add QP sum stats for received streams.

This is not implemented yet in any of the decoders.

BUG=webrtc:6541

Review-Url: https://codereview.webrtc.org/2649133005
Cr-Commit-Position: refs/heads/master@{#16475}
diff --git a/webrtc/modules/video_coding/test/test_util.h b/webrtc/modules/video_coding/test/test_util.h
index 45b88b9..86d3ecf 100644
--- a/webrtc/modules/video_coding/test/test_util.h
+++ b/webrtc/modules/video_coding/test/test_util.h
@@ -29,26 +29,18 @@
  public:
   virtual ~NullEvent() {}
 
-  virtual bool Set() { return true; }
+  bool Set() override { return true; }
 
-  virtual bool Reset() { return true; }
-
-  virtual webrtc::EventTypeWrapper Wait(unsigned long max_time) {  // NOLINT
+  webrtc::EventTypeWrapper Wait(unsigned long max_time) override {  // NOLINT
     return webrtc::kEventTimeout;
   }
-
-  virtual bool StartTimer(bool periodic, unsigned long time) {  // NOLINT
-    return true;
-  }
-
-  virtual bool StopTimer() { return true; }
 };
 
 class NullEventFactory : public webrtc::EventFactory {
  public:
   virtual ~NullEventFactory() {}
 
-  virtual webrtc::EventWrapper* CreateEvent() { return new NullEvent; }
+  webrtc::EventWrapper* CreateEvent() override { return new NullEvent; }
 };
 
 class FileOutputFrameReceiver : public webrtc::VCMReceiveCallback {
@@ -57,7 +49,8 @@
   virtual ~FileOutputFrameReceiver();
 
   // VCMReceiveCallback
-  virtual int32_t FrameToRender(webrtc::VideoFrame& video_frame);  // NOLINT
+  int32_t FrameToRender(webrtc::VideoFrame& video_frame,
+                        rtc::Optional<uint8_t> qp) override;
 
  private:
   std::string out_filename_;