Delete unneeded declaration of webrtc::MediaConstraintsInterface

Bug: webrtc:9239
Change-Id: I660623233c710cbe3353c2bee64d0267bc2fb92e
Reviewed-on: https://chromium-review.googlesource.com/c/1424803
Commit-Queue: Niels Möller <nisse@chromium.org>
Commit-Queue: Florent Castelli <orphis@chromium.org>
Auto-Submit: Niels Möller <nisse@chromium.org>
Reviewed-by: Florent Castelli <orphis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#624584}
diff --git a/content/renderer/media/webrtc/peer_connection_tracker.cc b/content/renderer/media/webrtc/peer_connection_tracker.cc
index 42ded54..87e4961 100644
--- a/content/renderer/media/webrtc/peer_connection_tracker.cc
+++ b/content/renderer/media/webrtc/peer_connection_tracker.cc
@@ -33,7 +33,6 @@
 #include "third_party/blink/public/web/web_local_frame.h"
 #include "third_party/blink/public/web/web_user_media_request.h"
 
-using webrtc::MediaConstraintsInterface;
 using webrtc::StatsReport;
 using webrtc::StatsReports;
 using blink::WebRTCPeerConnectionHandlerClient;