Fix all -Wnon-virtual-dtor warnings.

webrtc/p2p/base/turnserver.h

 /*
  *  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 126 matching lines @@
 };
 
 // An interface through which the MD5 credential hash can be retrieved.
 class TurnAuthInterface {
  public:
   // Gets HA1 for the specified user and realm.
   // HA1 = MD5(A1) = MD5(username:realm:password).
   // Return true if the given username and realm are valid, or false if not.
   virtual bool GetKey(const std::string& username, const std::string& realm,
                       std::string* key) = 0;
+  virtual ~TurnAuthInterface() = default;
 };
 
 // An interface enables Turn Server to control redirection behavior.
 class TurnRedirectInterface {
  public:
   virtual bool ShouldRedirect(const rtc::SocketAddress& address,
                               rtc::SocketAddress* out) = 0;
   virtual ~TurnRedirectInterface() {}
 };
 
@@ skipping 121 matching lines @@
   // For testing only. If this is non-zero, the next NONCE will be generated
   // from this value, and it will be reset to 0 after generating the NONCE.
   int64_t ts_for_next_nonce_ = 0;
 
   friend class TurnServerAllocation;
 };
 
 }  // namespace cricket
 
 #endif  // WEBRTC_P2P_BASE_TURNSERVER_H_