MediaCodecVideoEncoder: Add QP stats to Encoded callback for VP8.

BUG=

Review URL: https://codereview.webrtc.org/1884133003

Cr-Commit-Position: refs/heads/master@{#12435}
diff --git a/webrtc/api/java/jni/androidmediaencoder_jni.cc b/webrtc/api/java/jni/androidmediaencoder_jni.cc
index 1dfd56a..d70af65 100644
--- a/webrtc/api/java/jni/androidmediaencoder_jni.cc
+++ b/webrtc/api/java/jni/androidmediaencoder_jni.cc
@@ -1042,6 +1042,7 @@
           if (webrtc::vp8::GetQp(payload, payload_size, &qp)) {
             current_acc_qp_ += qp;
             quality_scaler_.ReportQP(qp);
+            image->qp_ = qp;
           }
         }
       } else if (codecType_ == kVideoCodecH264) {