Added class to subscribe to GCD notifications over XMPP.

remoting/signaling/push_notification_subscriber.cc

+// 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.
+
+#include "remoting/signaling/push_notification_subscriber.h"
+
+#include "base/bind.h"
+#include "base/callback.h"
+#include "remoting/base/logging.h"
+#include "remoting/signaling/iq_sender.h"
+#include "remoting/signaling/jid_util.h"
+#include "third_party/webrtc/libjingle/xmllite/xmlelement.h"
+
+namespace remoting {
+
+namespace {
+
+const char kNsGooglePush[] = "google:push";

[Sergey Ulanov, 2015/05/16 00:56:08]

maybe call it kGooglePushNamespace?

[John Williams, 2015/05/16 02:10:06]

Done.

+
+}  // namespace
+
+PushNotificationSubscriber::PushNotificationSubscriber(
+    SignalStrategy* signal_strategy,
+    const std::string& push_channel)
+    : signal_strategy_(signal_strategy), push_channel_(push_channel) {
+  signal_strategy_->AddListener(this);
+}
+
+PushNotificationSubscriber::~PushNotificationSubscriber() {
+  signal_strategy_->RemoveListener(this);
+}
+
+void PushNotificationSubscriber::OnSignalStrategyStateChange(
+    SignalStrategy::State state) {
+  if (state == SignalStrategy::CONNECTED) {
+    HOST_LOG << "Subscribing to push notifications on channel: "

[Sergey Ulanov, 2015/05/16 00:56:08]

I think this should be VLOG()

[John Williams, 2015/05/16 02:10:06]

Done.

+             << push_channel_ << ".";
+
+    std::string bare_jid;
+    SplitJidResource(signal_strategy_->GetLocalJid(), &bare_jid, nullptr);
+
+    // Build a subscription request.
+    buzz::XmlElement* subscribe_element =
+        new buzz::XmlElement(buzz::QName(kNsGooglePush, "subscribe"));
+    buzz::XmlElement* item_element =
+        new buzz::XmlElement(buzz::QName(kNsGooglePush, "item"));
+    subscribe_element->AddElement(item_element);
+    item_element->SetAttr(buzz::QName("", "channel"), push_channel_);

[Sergey Ulanov, 2015/05/16 00:56:08]

here and everywhere else: use std::string() instead of ""

[John Williams, 2015/05/16 02:10:06]

Done.

+    item_element->SetAttr(buzz::QName("", "from"), "");
+
+    // Send the request.
+    iq_sender_.reset(new IqSender(signal_strategy_));
+    iq_request_ = iq_sender_->SendIq(
+        "set", bare_jid, make_scoped_ptr(subscribe_element),
+        base::Bind(&PushNotificationSubscriber::OnSubscriptionResult,
+                   base::Unretained(this)));
+  }
+}
+
+bool PushNotificationSubscriber::OnSignalStrategyIncomingStanza(
+    const buzz::XmlElement* stanza) {
+  // Ignore all XMPP stanzas.
+  return false;
+}
+
+void PushNotificationSubscriber::OnSubscriptionResult(
+    IqRequest* request,
+    const buzz::XmlElement* response) {
+  std::string response_type = response->Attr(buzz::QName("", "type"));
+  if (response_type != "result") {
+    LOG(ERROR) << "Invalid response type for subscription: " << response_type;
+  }
+
+  // The IqSender and IqRequest are no longer needed after receiving a
+  // reply to the subscription request.
+  iq_request_.reset();
+  iq_sender_.reset();
+}
+
+}  // namespace remoting