Update internal SW codecs to return unique_ptrs

TBR=stefan@webrtc.org

Bug: webrtc:7925
Change-Id: I84239b071a2608d928f09b06809090eec5eafb14
Reviewed-on: https://webrtc-review.googlesource.com/21165
Commit-Queue: Magnus Jedvert <magjed@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20650}
diff --git a/modules/video_coding/generic_decoder.h b/modules/video_coding/generic_decoder.h
index 2c1206f..2d940d8 100644
--- a/modules/video_coding/generic_decoder.h
+++ b/modules/video_coding/generic_decoder.h
@@ -76,6 +76,7 @@
 
 class VCMGenericDecoder {
  public:
+  explicit VCMGenericDecoder(std::unique_ptr<VideoDecoder> decoder);
   explicit VCMGenericDecoder(VideoDecoder* decoder, bool isExternal = false);
   ~VCMGenericDecoder();