Small parameter name change from label->id in pc/mediastream.h.

TBR=deadbeef@webrtc.org

Bug: webrtc:8977
Change-Id: Ib80a868cbd55636fd5d41323e3b9913cf41070b8
Reviewed-on: https://webrtc-review.googlesource.com/65881
Reviewed-by: Seth Hampson <shampson@webrtc.org>
Commit-Queue: Seth Hampson <shampson@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22696}
diff --git a/pc/mediastream.h b/pc/mediastream.h
index 7f5d8e8..ab70e77 100644
--- a/pc/mediastream.h
+++ b/pc/mediastream.h
@@ -23,7 +23,7 @@
 
 class MediaStream : public Notifier<MediaStreamInterface> {
  public:
-  static rtc::scoped_refptr<MediaStream> Create(const std::string& label);
+  static rtc::scoped_refptr<MediaStream> Create(const std::string& id);
 
   std::string id() const override { return id_; }
 
@@ -40,7 +40,7 @@
   VideoTrackVector GetVideoTracks() override { return video_tracks_; }
 
  protected:
-  explicit MediaStream(const std::string& label);
+  explicit MediaStream(const std::string& id);
 
  private:
   template <typename TrackVector, typename Track>