Revert of Add EncodedImageCallback::OnEncodedImage(). (patchset #13 id:280001 of https://codereview.webrtc.org/2089773002/ )

Reason for revert:
broke internal tests

Original issue's description:
> Add EncodedImageCallback::OnEncodedImage().
>
> OnEncodedImage() is going to replace Encoded(), which is deprecated now.
> The new OnEncodedImage() returns Result struct that contains frame_id,
> which tells the encoder RTP timestamp for the frame.
>
> BUG=chromium:621691
> R=niklas.enbom@webrtc.org, sprang@webrtc.org, stefan@webrtc.org
>
> Committed: https://crrev.com/ad34dbe934d47f88011045671b4aea00dbd5a795
> Cr-Commit-Position: refs/heads/master@{#13613}

TBR=pbos@webrtc.org,mflodman@webrtc.org,sprang@webrtc.org,stefan@webrtc.org,niklas.enbom@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:621691

Review-Url: https://codereview.webrtc.org/2206743002
Cr-Commit-Position: refs/heads/master@{#13614}

webrtc/modules/video_coding/codecs/test/videoprocessor.h

@@ -230,7 +230,7 @@ class VideoProcessorImpl : public VideoProcessor {
    public:
     explicit VideoProcessorEncodeCompleteCallback(VideoProcessorImpl* vp)
         : video_processor_(vp) {}
-    Result OnEncodedImage(
+    int32_t Encoded(
         const webrtc::EncodedImage& encoded_image,
         const webrtc::CodecSpecificInfo* codec_specific_info,
         const webrtc::RTPFragmentationHeader* fragmentation) override;