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 f6a3b650a6b8aaf481fa941e3bbb777a09dc84b6..aa048d2711f912f2cf4f424ea00eb5c3132a10a5 100644
--- a/talk/app/webrtc/java/jni/androidmediaencoder_jni.cc
+++ b/talk/app/webrtc/java/jni/androidmediaencoder_jni.cc
@@ -785,8 +785,11 @@ 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))

[pbos-webrtc, 2015/10/15 11:56:01]

I think we can RTC_CHECK this one, the stream we produce should be trusted.

[åsapersson, 2015/10/16 09:33:59]

Added a RTC_DCHECK (call can proceed even if this fails).

[pbos-webrtc, 2015/10/16 09:50:55]

I think we want a CHECK to run out in the field, it'd be good to know if any
encoders start giving broken bitstreams.

+            quality_scaler_.ReportQP(qp);
+        }
       } else if (codecType_ == kVideoCodecH264) {
         if (scale_) {
           h264_bitstream_parser_.ParseBitstream(payload, payload_size);