Use I420Buffer rather than VideoFrameBuffer when writing pixels.

webrtc/api/androidvideotracksource.cc

Index: webrtc/api/androidvideotracksource.cc
diff --git a/webrtc/api/androidvideotracksource.cc b/webrtc/api/androidvideotracksource.cc
index 000337d34d6df8c8ccb46a0b2bd08372c4003f6a..f66e1e2f3e3d9434d05e7444aec758bfe5eec1db 100644
--- a/webrtc/api/androidvideotracksource.cc
+++ b/webrtc/api/androidvideotracksource.cc
@@ -115,7 +115,7 @@ void AndroidVideoTrackSource::OnByteBufferFrameCaptured(const void* frame_data,
     std::swap(rotated_width, rotated_height);
   }
 
-  rtc::scoped_refptr<webrtc::VideoFrameBuffer> buffer =
+  rtc::scoped_refptr<webrtc::I420Buffer> buffer =
       pre_scale_pool_.CreateBuffer(rotated_width, rotated_height);
 
   const uint8_t* y_plane = static_cast<const uint8_t*>(frame_data);