Add initial bitrate and frame resolution parameters to quality scaler.

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 5d22d72144413f0cb6477cdc38db082b1c272b5c..d0df19876ed182bd2927f6b6c7d02e47ae58f4da 100644
--- a/webrtc/modules/video_coding/codecs/vp8/vp8_impl.cc
+++ b/webrtc/modules/video_coding/codecs/vp8/vp8_impl.cc
@@ -601,7 +601,7 @@ int VP8EncoderImpl::InitEncode(const VideoCodec* inst,
   // internally.
   const int kDisabledBadQpThreshold = 64;
   quality_scaler_.Init(codec_.qpMax / QualityScaler::kDefaultLowQpDenominator,
-                       kDisabledBadQpThreshold, false);
+                       kDisabledBadQpThreshold, false, 0, 0, 0);

[pbos-webrtc, 2016/02/10 13:43:21]

I'd like to have this here as well, as I think the issue impacts all platforms.

[AlexG, 2016/02/10 19:07:16]

I think it is too early to enable this on all platforms - I guess BWE estimation
will converge pretty fast in typical use cases resulting in unnecessary 5
seconds delay when switching to HD.
I think to postpone this change in either follow up CL or until we can get
configurable windows.

[pbos-webrtc, 2016/02/10 19:12:27]

Initial bitrates, including keyframes, look bad at the initial 300k but VGA at
HD bitrate looks really good. The only thing I'm a bit curious of is if the good
QP thresholds always allow us to go back up.

I think you might postpone it but please put a TODO here. sprang@: Consider
checking this out. :)

   quality_scaler_.ReportFramerate(codec_.maxFramerate);
 
   // Only apply scaling to improve for single-layer streams. The scaling metrics