[Sync] Turn notifier::PushClient into an interface

jingle/notifier/listener/notification_defines.cc

 // Copyright (c) 2012 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 "jingle/notifier/listener/notification_defines.h"
 
+#include <cstddef>
+
 namespace notifier {
 
+Subscription::Subscription() {}
+Subscription::~Subscription() {}
+
+bool Subscription::Equals(const Subscription& other) const {
+  return channel == other.channel && from == other.from;
+}
+
+namespace {
+
+template <typename T>
+bool ListsEqual(const T& t1, const T& t2) {
+  if (t1.size() != t2.size()) {
+    return false;
+  }
+  for (size_t i = 0; i < t1.size(); ++i) {
+    if (!t1[i].Equals(t2[i])) {
+      return false;
+    }
+  }
+  return true;
+}
+
+}  // namespace
+
+bool SubscriptionListsEqual(const SubscriptionList& subscriptions1,
+                            const SubscriptionList& subscriptions2) {
+  return ListsEqual(subscriptions1, subscriptions2);
+}
+
+Recipient::Recipient() {}
+Recipient::~Recipient() {}
+
+bool Recipient::Equals(const Recipient& other) const {
+  return to == other.to && user_specific_data == other.user_specific_data;
+}
+
+bool RecipientListsEqual(const RecipientList& recipients1,
+                         const RecipientList& recipients2) {
+  return ListsEqual(recipients1, recipients2);
+}
+
 Notification::Notification() {}
 Notification::~Notification() {}
 
+bool Notification::Equals(const Notification& other) const {
+  return
+      channel == other.channel &&
+      data == other.data &&
+      RecipientListsEqual(recipients, other.recipients);
+}
+
 std::string Notification::ToString() const {
   return "{ channel: \"" + channel + "\", data: \"" + data + "\" }";
 }
 
 }  // namespace notifier