Fix all -Wnon-virtual-dtor warnings.

webrtc/api/api.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 48 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',
             '-Wno-unused-variable',
           ],
           '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.
           ],
         },
         {
           'target_name': 'libjingle_peerconnection_so',
@@ skipping 120 matching lines @@
         'webrtcsession.h',
         'webrtcsessiondescriptionfactory.cc',
         'webrtcsessiondescriptionfactory.h',
       ],
       # 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_cc!': [
-        '-Wnon-virtual-dtor',
         '-Woverloaded-virtual',
       ],
       'conditions': [
         ['clang==1', {
           'cflags!': [
             '-Wextra',
           ],
           'xcode_settings': {
             'WARNING_CFLAGS!': ['-Wextra'],
           },
@@ skipping 16 matching lines @@
               'AdditionalOptions': [
                 '-Wno-sign-compare',
               ],
             },
           },
         }],
       ],
     },  # target libjingle_peerconnection
   ],  # targets
 }