Add Network Quality Estimator (NQE) pref manager

net/nqe/network_id.h

 // Copyright 2016 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.
 
 #ifndef NET_NQE_NETWORK_ID_H_
 #define NET_NQE_NETWORK_ID_H_
 
 #include <string>
 #include <tuple>
 
 #include "net/base/net_export.h"
 #include "net/base/network_change_notifier.h"
 
+namespace {
+const char kValueSeparator[] = ",";
+}
+
 namespace net {
 namespace nqe {
 namespace internal {
 
 // NetworkID is used to uniquely identify a network.
 // For the purpose of network quality estimation and caching, a network is
 // uniquely identified by a combination of |type| and
 // |id|. This approach is unable to distinguish networks with
 // same name (e.g., different Wi-Fi networks with same SSID).
 // This is a protected member to expose it to tests.
 struct NET_EXPORT_PRIVATE NetworkID {
   NetworkID(NetworkChangeNotifier::ConnectionType type, const std::string& id)
       : type(type), id(id) {}
   NetworkID(const NetworkID& other) : type(other.type), id(other.id) {}
   ~NetworkID() {}
 
   NetworkID& operator=(const NetworkID& other) {
     type = other.type;
     id = other.id;
     return *this;
   }
 
   // Overloaded to support ordered collections.
   bool operator<(const NetworkID& other) const {
     return std::tie(type, id) < std::tie(other.type, other.id);
   }
 
+  std::string ToString() const {
+    return id + kValueSeparator +

[bengr, 2016/09/22 23:35:46]

It seems like overill to define kValueSeparator. I would either do:

return id + "," + ...

or 

return StringPrintf("%s,%s", id.c_str(), ...

[tbansal1, 2016/09/23 17:10:32]

The value separator is going to be used soon (in the next cl) in a different
function when reading back the prefs and deserializing it. So, it is better to
keep it in a common place, but I can remove it for now, if you feel strongly
about it.

[bengr, 2016/09/23 20:31:06]

Nah. If you're gonna use it, keep it.

[tbansal1, 2016/09/23 20:50:13]

Acknowledged.

+           NetworkChangeNotifier::ConnectionTypeToString(type);
+  }
+
   // Connection type of the network.
   NetworkChangeNotifier::ConnectionType type;
 
   // Name of this network. This is set to:
   // - Wi-Fi SSID if the device is connected to a Wi-Fi access point and the
   //   SSID name is available, or
   // - MCC/MNC code of the cellular carrier if the device is connected to a
   //   cellular network, or
   // - "Ethernet" in case the device is connected to ethernet.
   // - An empty string in all other cases or if the network name is not
   //   exposed by platform APIs.
   std::string id;
 };
 
 }  // namespace internal
 }  // namespace nqe
 }  // namespace net
 
 #endif  // NET_NQE_NETWORK_QUALITY_ESTIMATOR_H_