[WIP] attempt to allow chrome OS to inject its wifi data provider

content/browser/geolocation/device_data_provider.cc

-// Copyright (c) 2011 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/device_data_provider.h"
-
-// statics
-template<> DeviceDataProvider<WifiData>*
-    DeviceDataProvider<WifiData>::instance_ = NULL;
-template<> DeviceDataProvider<WifiData>::ImplFactoryFunction
-    DeviceDataProvider<WifiData>::factory_function_ = DefaultFactoryFunction;
-
-AccessPointData::AccessPointData()
-    : radio_signal_strength(kint32min),
-      channel(kint32min),
-      signal_to_noise(kint32min) {
-}
-
-AccessPointData::~AccessPointData() {}
-
-WifiData::WifiData() {}
-
-WifiData::~WifiData() {}
-
-bool WifiData::DiffersSignificantly(const WifiData& other) const {
-  // More than 4 or 50% of access points added or removed is significant.
-  static const size_t kMinChangedAccessPoints = 4;
-  const size_t min_ap_count =
-      std::min(access_point_data.size(), other.access_point_data.size());
-  const size_t max_ap_count =
-      std::max(access_point_data.size(), other.access_point_data.size());
-  const size_t difference_threadhold = std::min(kMinChangedAccessPoints,
-                                                min_ap_count / 2);
-  if (max_ap_count > min_ap_count + difference_threadhold)
-    return true;
-  // Compute size of interesction of old and new sets.
-  size_t num_common = 0;
-  for (AccessPointDataSet::const_iterator iter = access_point_data.begin();
-       iter != access_point_data.end();
-       iter++) {
-    if (other.access_point_data.find(*iter) !=
-        other.access_point_data.end()) {
-      ++num_common;
-    }
-  }
-  DCHECK(num_common <= min_ap_count);
-
-  // Test how many have changed.
-  return max_ap_count > num_common + difference_threadhold;
-}