Delete deprecated PeerConnection methods, and corresponding using declarations.

webrtc/pc/peerconnection_unittest.cc

Index: webrtc/pc/peerconnection_unittest.cc
diff --git a/webrtc/pc/peerconnection_unittest.cc b/webrtc/pc/peerconnection_unittest.cc
index f62d30baf4044efdb7bbebd768fe9387dbb49b15..e5e310ea0fd17be4fdf8bddfbc3a1bbd942bb994 100644
--- a/webrtc/pc/peerconnection_unittest.cc
+++ b/webrtc/pc/peerconnection_unittest.cc
@@ -183,13 +183,6 @@ class PeerConnectionTestClient : public webrtc::PeerConnectionObserver,
                                  public ObserverInterface,
                                  public rtc::MessageHandler {
  public:
-  // We need these using declarations because there are two versions of each of
-  // the below methods and we only override one of them.
-  // TODO(deadbeef): Remove once there's only one version of the methods.
-  using PeerConnectionObserver::OnAddStream;
-  using PeerConnectionObserver::OnRemoveStream;
-  using PeerConnectionObserver::OnDataChannel;
-
   // If |config| is not provided, uses a default constructed RTCConfiguration.
   static PeerConnectionTestClient* CreateClientWithDtlsIdentityStore(
       const std::string& id,