Make dbus-based wifi data provider optional on linux

content/browser/geolocation/empty_wifi_data_provider.cc

 // Copyright 2013 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.
 
 #include "content/browser/geolocation/empty_wifi_data_provider.h"
 
 namespace content {
 
 EmptyWifiDataProvider::EmptyWifiDataProvider() {
 }
 
 EmptyWifiDataProvider::~EmptyWifiDataProvider() {
 }
 
 bool EmptyWifiDataProvider::GetData(WifiData* data) {
   DCHECK(data);
   // This is all the data we can get - nothing.
   return true;
 }
 
-// Only define for platforms that lack a real wifi data provider.
-#if !defined(OS_WIN) && !defined(OS_MACOSX) && !defined(OS_LINUX)
 // static
 WifiDataProviderImplBase* WifiDataProvider::DefaultFactoryFunction() {
   return new EmptyWifiDataProvider();
 }
-#endif
 
 }  // namespace content