Renamed FrameObject to EncodedFrame.

The plan is to:
 1. Move FrameObject to api/video.
 2. Rename FrameObject to EncodedFrame.
 3. Move EncodedFrame out of the video_coding namespace.

This is the 2nd CL.

Bug: webrtc:8909
Change-Id: I5e76a0a3b306156b8bc1de67834b4adf14bebef9
Reviewed-on: https://webrtc-review.googlesource.com/56182
Commit-Queue: Philip Eliasson <philipel@webrtc.org>
Commit-Queue: Tommi <tommi@webrtc.org>
Reviewed-by: Niels Moller <nisse@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22158}
diff --git a/video/rtp_video_stream_receiver.h b/video/rtp_video_stream_receiver.h
index 71cb5db..da8b837 100644
--- a/video/rtp_video_stream_receiver.h
+++ b/video/rtp_video_stream_receiver.h
@@ -135,7 +135,7 @@
 
   // Implements OnCompleteFrameCallback.
   void OnCompleteFrame(
-      std::unique_ptr<video_coding::FrameObject> frame) override;
+      std::unique_ptr<video_coding::EncodedFrame> frame) override;
 
   void OnRttUpdate(int64_t avg_rtt_ms, int64_t max_rtt_ms) override;