Revert "Removed VideoDecoderFactory::LegacyCreateVideoDecoder and VideoReceiveStream::Config::stream_id."

This reverts commit 4ba1044bae750ab8ee47b359c21f672386b7c3cd.

Reason for revert: Downstream projects require some updates.

Original change's description:
> Removed VideoDecoderFactory::LegacyCreateVideoDecoder and VideoReceiveStream::Config::stream_id.
> 
> Bug: webrtc:9106
> Change-Id: I7fa84095732c33d136a9354ae4f09266cffcf877
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/180020
> Reviewed-by: Henrik Andreassson <henrika@webrtc.org>
> Commit-Queue: Philip Eliasson <philipel@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#31793}

TBR=henrika@webrtc.org,magjed@webrtc.org,philipel@webrtc.org,mflodman@webrtc.org

Change-Id: I8c980266334cc9871b9076713da3c4df8f73f8ce
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:9106
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/180344
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Commit-Queue: Philip Eliasson <philipel@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31794}
diff --git a/api/video_codecs/video_decoder_factory.h b/api/video_codecs/video_decoder_factory.h
index 4809bee..e4d83c2 100644
--- a/api/video_codecs/video_decoder_factory.h
+++ b/api/video_codecs/video_decoder_factory.h
@@ -34,6 +34,12 @@
   virtual std::unique_ptr<VideoDecoder> CreateVideoDecoder(
       const SdpVideoFormat& format) = 0;
 
+  // Note: Do not call or override this method! This method is a legacy
+  // workaround and is scheduled for removal without notice.
+  virtual std::unique_ptr<VideoDecoder> LegacyCreateVideoDecoder(
+      const SdpVideoFormat& format,
+      const std::string& receive_stream_id);
+
   virtual ~VideoDecoderFactory() {}
 };