Add stats for average QP per frame for VP8 (for received video streams).

talk/app/webrtc/java/jni/androidmediaencoder_jni.cc

Index: talk/app/webrtc/java/jni/androidmediaencoder_jni.cc
diff --git a/talk/app/webrtc/java/jni/androidmediaencoder_jni.cc b/talk/app/webrtc/java/jni/androidmediaencoder_jni.cc
index d2ec5528341cf423233e2cc76d01bd4e395742f8..3bbf6827f52ded2a38f03c5f2bd91ce1cb1d8748 100644
--- a/talk/app/webrtc/java/jni/androidmediaencoder_jni.cc
+++ b/talk/app/webrtc/java/jni/androidmediaencoder_jni.cc
@@ -795,8 +795,11 @@ bool MediaCodecVideoEncoder::DeliverPendingOutputs(JNIEnv* jni) {
         header.fragmentationLength[0] = image->_length;
         header.fragmentationPlType[0] = 0;
         header.fragmentationTimeDiff[0] = 0;
-        if (scale_)
-          quality_scaler_.ReportQP(webrtc::vp8::GetQP(payload));
+        if (scale_) {
+          int qp;
+          if (webrtc::vp8::GetQp(payload, payload_size, &qp))
+            quality_scaler_.ReportQP(qp);
+        }
       } else if (codecType_ == kVideoCodecH264) {
         if (scale_) {
           h264_bitstream_parser_.ParseBitstream(payload, payload_size);