Add QP for libvpx VP8 decoder.

webrtc/modules/video_coding/codecs/vp8/vp8_impl.cc

Index: webrtc/modules/video_coding/codecs/vp8/vp8_impl.cc
diff --git a/webrtc/modules/video_coding/codecs/vp8/vp8_impl.cc b/webrtc/modules/video_coding/codecs/vp8/vp8_impl.cc
index 2fbceb1d7904b8a5ff7714a30fcce6afe1bf9266..cb6102128f1d0f7b60d548254e1853f504a72aee 100644
--- a/webrtc/modules/video_coding/codecs/vp8/vp8_impl.cc
+++ b/webrtc/modules/video_coding/codecs/vp8/vp8_impl.cc
@@ -1145,7 +1145,9 @@ int VP8DecoderImpl::Decode(const EncodedImage& input_image,
   }
 
   img = vpx_codec_get_frame(decoder_, &iter);
-  ret = ReturnFrame(img, input_image._timeStamp, input_image.ntp_time_ms_);
+  int qp;
+  vpx_codec_control(decoder_, VPXD_GET_LAST_QUANTIZER, &qp);

[sakal, 2017/02/16 12:44:49]

This method can return failure in theory. However, in practice it only happens
if it is not supplied a valid int pointer. I would prefer not adding dead code
for handling this. WDYT?

+  ret = ReturnFrame(img, input_image._timeStamp, input_image.ntp_time_ms_, qp);
   if (ret != 0) {
     // Reset to avoid requesting key frames too often.
     if (ret < 0 && propagation_cnt_ > 0)
@@ -1205,7 +1207,8 @@ int VP8DecoderImpl::Decode(const EncodedImage& input_image,
 
 int VP8DecoderImpl::ReturnFrame(const vpx_image_t* img,
                                 uint32_t timestamp,
-                                int64_t ntp_time_ms) {
+                                int64_t ntp_time_ms,
+                                int qp) {
   if (img == NULL) {
     // Decoder OK and NULL image => No show frame
     return WEBRTC_VIDEO_CODEC_NO_OUTPUT;
@@ -1232,9 +1235,8 @@ int VP8DecoderImpl::ReturnFrame(const vpx_image_t* img,
 
   VideoFrame decoded_image(buffer, timestamp, 0, kVideoRotation_0);
   decoded_image.set_ntp_time_ms(ntp_time_ms);
-  int ret = decode_complete_callback_->Decoded(decoded_image);
-  if (ret != 0)
-    return ret;
+  decode_complete_callback_->Decoded(decoded_image, rtc::Optional<int32_t>(),
+                                     rtc::Optional<uint8_t>(qp));
 
   // Remember image format for later
   image_format_ = img->fmt;