[Sync] Turn notifier::PushClient into an interface

jingle/notifier/listener/non_blocking_push_client.h

Index: jingle/notifier/listener/non_blocking_push_client.h
diff --git a/jingle/notifier/listener/non_blocking_push_client.h b/jingle/notifier/listener/non_blocking_push_client.h
new file mode 100644
index 0000000000000000000000000000000000000000..ca572291928f05f02d88e65a1fd20d3cf9d93585
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+++ b/jingle/notifier/listener/non_blocking_push_client.h
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+// 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 JINGLE_NOTIFIER_LISTENER_NON_BLOCKING_PUSH_CLIENT_H_
+#define JINGLE_NOTIFIER_LISTENER_NON_BLOCKING_PUSH_CLIENT_H_
+
+#include "base/basictypes.h"
+#include "base/callback_forward.h"
+#include "base/compiler_specific.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
+#include "base/observer_list.h"
+#include "base/threading/non_thread_safe.h"
+#include "jingle/notifier/listener/push_client.h"
+
+namespace base {
+class SingleThreadTaskRunner;
+} // namespace base
+
+namespace notifier {
+
+// This class implements a PushClient that doesn't block; it delegates
+// to another blocking PushClient on a separate thread.
+//
+// This class must be used on a single thread.
+class NonBlockingPushClient : public PushClient {
+ public:
+  // The type for a function that creates a (blocking) PushClient.
+  // Will be called on the delegate task runner.
+  typedef base::Callback<scoped_ptr<PushClient>()>
+      CreateBlockingPushClientCallback;
+
+  // Runs the given callback on the given task runner, and delegates
+  // to that PushClient.
+  explicit NonBlockingPushClient(
+      const scoped_refptr<base::SingleThreadTaskRunner>& delegate_task_runner,
+      const CreateBlockingPushClientCallback&
+          create_blocking_push_client_callback);
+  virtual ~NonBlockingPushClient();
+
+  // PushClient implementation.
+  virtual void AddObserver(PushClientObserver* observer) OVERRIDE;
+  virtual void RemoveObserver(PushClientObserver* observer) OVERRIDE;
+  virtual void UpdateSubscriptions(
+      const SubscriptionList& subscriptions) OVERRIDE;
+  virtual void UpdateCredentials(
+      const std::string& email, const std::string& token) OVERRIDE;
+  virtual void SendNotification(const Notification& notification) OVERRIDE;
+
+ private:
+  class Core;
+
+  void OnNotificationStateChange(bool notifications_enabled);
+  void OnIncomingNotification(const Notification& notification);
+
+  base::NonThreadSafe non_thread_safe_;
+  base::WeakPtrFactory<NonBlockingPushClient> weak_ptr_factory_;
+  const scoped_refptr<base::SingleThreadTaskRunner> delegate_task_runner_;
+  const scoped_refptr<Core> core_;
+
+  ObserverList<PushClientObserver> observers_;
+
+  DISALLOW_COPY_AND_ASSIGN(NonBlockingPushClient);
+};
+
+}  // namespace notifier
+
+#endif  // JINGLE_NOTIFIER_LISTENER_NON_BLOCKING_PUSH_CLIENT_H_