WebRTC: Fix and enable -Woverloaded-virtual warnings.

webrtc/api/peerconnection_unittest.cc

 /*
  *  Copyright 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 170 matching lines @@
  private:
   bool first_packet_received_ = false;
   cricket::MediaType expected_media_type_;
 };
 
 class PeerConnectionTestClient : public webrtc::PeerConnectionObserver,
                                  public SignalingMessageReceiver,
                                  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,
       const MediaConstraintsInterface* constraints,
       const PeerConnectionFactory::Options* options,
       const PeerConnectionInterface::RTCConfiguration* config,
       std::unique_ptr<rtc::RTCCertificateGeneratorInterface> cert_generator,
       bool prefer_constraint_apis,
       rtc::Thread* network_thread,
       rtc::Thread* worker_thread) {
@@ skipping 2570 matching lines @@
   server.urls.push_back("turn:hostname2");
   servers.push_back(server);
   EXPECT_TRUE(webrtc::ParseIceServers(servers, &stun_servers_, &turn_servers_));
   EXPECT_EQ(2U, turn_servers_.size());
   EXPECT_NE(turn_servers_[0].priority, turn_servers_[1].priority);
 }
 
 #endif // if !defined(THREAD_SANITIZER)
 
 }  // namespace