Fix all -Wnon-virtual-dtor warnings.

webrtc/api/api_tests.gyp

 # Copyright (c) 2015 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.
 
 {
   'includes': [ '../build/common.gypi', ],
@@ skipping 54 matching lines @@
       ],
       # TODO(kjellander): Make the code compile without disabling these flags.
       # See https://bugs.chromium.org/p/webrtc/issues/detail?id=3307
       'cflags': [
         '-Wno-sign-compare',
       ],
       'cflags!': [
         '-Wextra',
       ],
       'cflags_cc!': [
-        '-Wnon-virtual-dtor',
         '-Woverloaded-virtual',
       ],
       'msvs_disabled_warnings': [
         4245,  # conversion from 'int' to 'size_t', signed/unsigned mismatch.
         4267,  # conversion from 'size_t' to 'int', possible loss of data.
         4389,  # signed/unsigned mismatch.
       ],
       'conditions': [
         ['clang==1', {
           # TODO(kjellander): Make the code compile without disabling these flags.
@@ skipping 112 matching lines @@
             '../build/isolate.gypi',
           ],
           'sources': [
             'peerconnection_unittests.isolate',
           ],
         },
       ],  # targets
     }],  # test_isolation_mode != "noop"
   ],  # conditions
 }