Plumb invalidations from Tango to the extensions code for the Push Messaging API.

chrome/browser/extensions/api/push_messaging/push_messaging_invalidation_handler.h

+// 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.
+
+#ifndef CHROME_BROWSER_EXTENSIONS_API_PUSH_MESSAGING_PUSH_MESSAGING_INVALIDATION_HANDLER_H_
+#define CHROME_BROWSER_EXTENSIONS_API_PUSH_MESSAGING_PUSH_MESSAGING_INVALIDATION_HANDLER_H_
+
+#include <set>
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"

[Pete Williamson, 2012/08/13 18:24:09]

It's a bit scary that we need to have some compiler specific behavior.  A
comment might help the maintenance programmer understand why we need this header
file.

[dcheng, 2012/08/13 20:44:14]

It is used for the OVERRIDE keyword. Since this is so prevalent, it's generally
not commented upon.

+#include "base/threading/thread_checker.h"
+#include "chrome/browser/extensions/api/push_messaging/push_messaging_invalidation_mapper.h"
+#include "sync/notifier/sync_notifier_observer.h"
+
+class InvalidationService;
+

[Pete Williamson, 2012/08/13 18:24:09]

It might be nice to replace the word Invalidations in file and class names with
"Message", or "Notification" or "Event".  Invalidations is a kind of strange
concept for the maintenance programmer to understand, and an artifact of the
underlying layer.

[dcheng, 2012/08/13 20:44:14]

Notification, Message, and Event are all a little too generic here IMO.
"Invalidation" fits well since this is the class that maps between the
invalidation model and the extension API model.

+namespace extensions {
+
+class PushMessagingInvalidationHandlerObserver;
+
+// This class maps extension IDs to their corresponding object IDs, manages the
+// Tango registrations, and dispatches callbacks for any invalidations received.

[akalin, 2012/08/10 23:07:10]

tango is an internal code name.  maybe 'invalidation registrations'?

[dcheng, 2012/08/13 20:44:14]

Done. "tango" is mentioned in the google-cache-invalidation repository though
which is why I thought it'd be OK.

+class PushMessagingInvalidationHandler : public PushMessagingInvalidationMapper,
+                                         public syncer::SyncNotifierObserver {
+ public:
+  // |extension_ids| is the set of extension IDs for which push messaging is
+  // enabled.

[Pete Williamson, 2012/08/13 18:24:09]

It might be good to comment on the ownership of the service and observer objects
- are they taken over by the handler, or assumed to remain valid over the
lifetime of the Handler?

[dcheng, 2012/08/13 20:44:14]

Done.

+  PushMessagingInvalidationHandler(
+      InvalidationService* service,
+      PushMessagingInvalidationHandlerObserver* observer,
+      const std::set<std::string>& extension_ids);
+  virtual ~PushMessagingInvalidationHandler();
+
+  // PushMessagingInvalidationMapper implementation.
+  virtual void RegisterExtension(const std::string& extension_id) OVERRIDE;
+  virtual void UnregisterExtension(const std::string& extension_id) OVERRIDE;
+
+  // SyncNotifierObserver implementation.

[Pete Williamson, 2012/08/13 18:24:09]

A bit more comment here about what a SyncNotifierObserver is might help. 
"Observes Notifications coming from Sync Layer, and routes them" perhaps?

[dcheng, 2012/08/13 20:44:14]

Usually the documentation for the interface lives in the file that defines the
interface. Otherwise it'd create a lot of duplicate comments.

+  virtual void OnNotificationsEnabled() OVERRIDE;
+  virtual void OnNotificationsDisabled(
+      syncer::NotificationsDisabledReason reason) OVERRIDE;
+  virtual void OnIncomingNotification(
+      const syncer::ObjectIdPayloadMap& id_payloads,
+      syncer::IncomingNotificationSource source) OVERRIDE;
+
+ private:
+  base::ThreadChecker thread_checker_;
+  InvalidationService* service_;
+  syncer::ObjectIdSet registered_ids_;
+  PushMessagingInvalidationHandlerObserver* observer_;
+
+  DISALLOW_COPY_AND_ASSIGN(PushMessagingInvalidationHandler);
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_API_PUSH_MESSAGING_PUSH_MESSAGING_INVALIDATION_HANDLER_H_