Add QP for libvpx VP8 decoder.

webrtc/modules/video_coding/codecs/test/videoprocessor.h

Index: webrtc/modules/video_coding/codecs/test/videoprocessor.h
diff --git a/webrtc/modules/video_coding/codecs/test/videoprocessor.h b/webrtc/modules/video_coding/codecs/test/videoprocessor.h
index 778cc1d5994f1b8bcb01a76cf4e718830f81a7b3..64aabae3340e0b5362769e0ccbbb7364ff060699 100644
--- a/webrtc/modules/video_coding/codecs/test/videoprocessor.h
+++ b/webrtc/modules/video_coding/codecs/test/videoprocessor.h
@@ -252,9 +252,7 @@ class VideoProcessorImpl : public VideoProcessor {
     }
     void Decoded(VideoFrame& frame,
                  rtc::Optional<int32_t> decode_time_ms,
-                 rtc::Optional<uint8_t> qp) override {
-      RTC_NOTREACHED();
-    }
+                 rtc::Optional<uint8_t> qp) override;
 
    private:
     VideoProcessorImpl* video_processor_;