Added class to subscribe to GCD notifications over XMPP.

remoting/host/gcd_notification_subscriber.cc

+// Copyright (c) 2015 The Chromium Authors. All rights reserved.

[Sergey Ulanov, 2015/05/07 18:22:38]

remove (c)

[John Williams, 2015/05/15 00:51:12]

Done.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "remoting/host/gcd_notification_subscriber.h"
+
+#include "base/bind.h"
+#include "base/callback.h"
+#include "remoting/base/logging.h"
+#include "remoting/signaling/iq_sender.h"
+#include "third_party/webrtc/libjingle/xmllite/xmlelement.h"
+
+namespace remoting {
+
+namespace {
+
+const char kNsGooglePush[] = "google:push";
+
+}  // namespace
+
+GcdNotificationSubscriber::GcdNotificationSubscriber(
+    SignalStrategy* signal_strategy)
+    : signal_strategy_(signal_strategy) {
+  signal_strategy_->AddListener(this);
+}
+
+GcdNotificationSubscriber::~GcdNotificationSubscriber() {
+  signal_strategy_->RemoveListener(this);
+}
+
+void GcdNotificationSubscriber::OnSignalStrategyStateChange(
+    SignalStrategy::State state) {
+  if (state == SignalStrategy::CONNECTED) {
+    DLOG(INFO) << "subscribing to GCD command notifications";

[Sergey Ulanov, 2015/05/07 18:22:38]

nit: s/subscribing/Subscribing/
Add . at the end

[John Williams, 2015/05/15 00:51:12]

Done.

+
+    // Convert full JID to bare JID.
+    std::string bare_jid = signal_strategy_->GetLocalJid();
+    size_t slash_index = bare_jid.find('/');

[Sergey Ulanov, 2015/05/07 18:22:38]

There are at least two other places where we need to separate JID resource_id: 
https://code.google.com/p/chromium/codesearch#chromium/src/remoting/protocol/...
and 
https://code.google.com/p/chromium/codesearch#chromium/src/remoting/signaling...

Maybe it's worth adding a helper method for this in
remoting/signaling/jid_util.h

[John Williams, 2015/05/15 00:51:12]

Done.

+    if (slash_index != std::string::npos) {
+      bare_jid.resize(slash_index);
+    }
+
+    // Build a subscription request.
+    buzz::XmlElement* itemElement =

[Sergey Ulanov, 2015/05/07 18:22:38]

item_element

[John Williams, 2015/05/15 00:51:12]

Done.

+        new buzz::XmlElement(buzz::QName(kNsGooglePush, "item"));
+    itemElement->SetAttr(buzz::QName("", "channel"), "cloud_devices");
+    itemElement->SetAttr(buzz::QName("", "from"), "");
+    buzz::XmlElement* subscribeElement =

[Sergey Ulanov, 2015/05/07 18:22:38]

subscribe_element.
In other code that builds XmlElement we normally create elements in the same
order in which they appear in XML and I suggest following the same pattern here,
i.e.:

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);

This makes it easier to read this code.

[John Williams, 2015/05/15 00:51:11]

Done.

+        new buzz::XmlElement(buzz::QName(kNsGooglePush, "subscribe"));
+    subscribeElement->AddElement(itemElement);
+
+    // Send the request.
+    iq_sender_.reset(new IqSender(signal_strategy_));
+    iq_request_ = iq_sender_->SendIq(
+        "set", bare_jid, make_scoped_ptr(subscribeElement),
+        base::Bind(&GcdNotificationSubscriber::OnSubscriptionResult,
+                   base::Unretained(this)));
+  }
+}
+
+bool GcdNotificationSubscriber::OnSignalStrategyIncomingStanza(
+    const buzz::XmlElement* stanza) {
+  // Ignore all XMPP stanzas.
+  return false;
+}
+
+void GcdNotificationSubscriber::OnSubscriptionResult(
+    IqRequest* request,
+    const buzz::XmlElement* response) {
+  DCHECK_EQ(response->Attr(buzz::QName("", "type")), "result")

[Sergey Ulanov, 2015/05/07 18:22:38]

This shouldn't be DCHECK. Crashing in response to a message received from a
remote service is never right thing to do, even in debug builds. You also don't
want to ignore the error in Release builds. I think you always want to check the
result and log an error if the request has failed.

[John Williams, 2015/05/15 00:51:12]

Done.

+      << "invalid 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