Move common VideoPacket initialization into VideoEncoderHelper.

remoting/codec/video_encoder_vpx.h

Index: remoting/codec/video_encoder_vpx.h
diff --git a/remoting/codec/video_encoder_vpx.h b/remoting/codec/video_encoder_vpx.h
index 133b754ec4c0e7554a37f6adde472a285217ca03..80e69db0cd139802e6ced9a738d376211938f956 100644
--- a/remoting/codec/video_encoder_vpx.h
+++ b/remoting/codec/video_encoder_vpx.h
@@ -9,6 +9,7 @@
 #include "base/time/time.h"
 #include "remoting/codec/scoped_vpx_codec.h"
 #include "remoting/codec/video_encoder.h"
+#include "remoting/codec/video_encoder_helper.h"
 
 typedef struct vpx_image vpx_image_t;
 
@@ -68,6 +69,9 @@ class VideoEncoderVpx : public VideoEncoder {
   int active_map_width_;
   int active_map_height_;
 
+  // Used to help initialize VideoPackets from DesktopFrames.
+  VideoEncoderHelper helper_;
+
   DISALLOW_COPY_AND_ASSIGN(VideoEncoderVpx);
 };