Fix all -Wnon-virtual-dtor warnings.

webrtc/p2p/p2p.gyp

Index: webrtc/p2p/p2p.gyp
diff --git a/webrtc/p2p/p2p.gyp b/webrtc/p2p/p2p.gyp
index 5c9a575f8f24b13e6633aa0bf57efeb04352c4cf..2b27e44986682a47727549d9b0839373a3704fbf 100644
--- a/webrtc/p2p/p2p.gyp
+++ b/webrtc/p2p/p2p.gyp
@@ -16,9 +16,6 @@
         '<(webrtc_root)/base/base.gyp:rtc_base',
         '<(webrtc_root)/common.gyp:webrtc_common',
       ],
-      'cflags_cc!': [
-        '-Wnon-virtual-dtor',
-      ],
       'sources': [
         'base/asyncstuntcpsocket.cc',
         'base/asyncstuntcpsocket.h',
@@ -84,9 +81,6 @@
         'client/socketmonitor.h',
       ],
       'direct_dependent_settings': {
-        'cflags_cc!': [
-          '-Wnon-virtual-dtor',
-        ],
         'defines': [
           'FEATURE_ENABLE_VOICEMAIL',
         ],
@@ -125,9 +119,6 @@
         '<(webrtc_root)/base/base.gyp:rtc_base',
         '<(webrtc_root)/common.gyp:webrtc_common',
       ],
-      'cflags_cc!': [
-        '-Wnon-virtual-dtor',
-      ],
       'sources': [
         'stunprober/stunprober.cc',
       ],
@@ -139,9 +130,6 @@
         'libstunprober',
         'rtc_p2p'
       ],
-      'cflags_cc!': [
-        '-Wnon-virtual-dtor',
-      ],
       'sources': [
         'stunprober/main.cc',
       ],