Add QP for libvpx VP8 decoder.

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

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 234 matching lines @@
     explicit VideoProcessorDecodeCompleteCallback(VideoProcessorImpl* vp)
         : video_processor_(vp) {}
     int32_t Decoded(webrtc::VideoFrame& image) override;
     int32_t Decoded(webrtc::VideoFrame& image,
                     int64_t decode_time_ms) override {
       RTC_NOTREACHED();
       return -1;
     }
     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_;
   };
 };
 
 }  // namespace test
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_VIDEO_CODING_CODECS_TEST_VIDEOPROCESSOR_H_