Introduce an 'ENABLE_WEBSOCKETS' define in //net.

net/net_common.gypi

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   # This target is included by 'net' target.
   'type': '<(component)',
   'variables': { 'enable_wexit_time_destructors': 1, },
   'dependencies': [
     '../base/base.gyp:base',
@@ skipping 194 matching lines @@
     ],
     # client_cert_store_nss.c requires NSS_CmpCertChainWCANames from NSS's
     # libssl, but our bundled copy is not built in OpenSSL ports. Pull that
     # file in directly.
     [ 'use_nss_certs == 1', {
         'sources': [
           'third_party/nss/ssl/cmpcert.c',
         ],
     }],
     [ 'enable_websockets == 1', {
+        'defines': ['ENABLE_WEBSOCKETS'],
         'sources': ['<@(net_websockets_sources)']
     }],
     [ 'enable_mdns != 1', {
         'sources!' : [
           'dns/mdns_cache.cc',
           'dns/mdns_cache.h',
           'dns/mdns_client.cc',
           'dns/mdns_client.h',
           'dns/mdns_client_impl.cc',
           'dns/mdns_client_impl.h',
@@ skipping 131 matching lines @@
         ['include', '^proxy/proxy_server_mac\\.cc$'],
       ],
     }],
     ['OS == "ios"', {
       'sources/': [
         ['include', '^cert/test_root_certs_mac\\.cc$'],
       ],
     }],
   ],
 }