Blimp: define HeliumTransport/HeliumStream interfaces.

blimp/net/helium/helium_transport.h

+// Copyright 2016 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 BLIMP_NET_HELIUM_HELIUM_TRANSPORT_H_
+#define BLIMP_NET_HELIUM_HELIUM_TRANSPORT_H_
+
+#include <memory>
+
+#include "base/callback.h"
+
+namespace blimp {
+
+// Abstract interface for a HeliumStream factory. Subclasses can use this
+// interface to encapsulate transport-specific connection semantics.
+class HeliumTransport {

[perumaal, 2016/09/29 19:13:50]

Just to make sure. Would this initially wrap a BlimpTransport internally?

[Kevin M, 2016/09/29 21:18:40]

That's a possibility, then we'd have a HeliumStream wrap a MessagePort.

+ public:
+  // The HeliumStream is assumed to be authenticated and ready to use.
+  // |stream| is nullptr if the connection attempt failed.
+  using ConnectCallback =
+      base::Callback<void(std::unique_ptr<HeliumStream> stream)>;
+
+  // Asynchronously attempts to connect a new HeliumStream.
+  virtual void Connect(const ConnectCallback& connect_cb) = 0;

[scf, 2016/09/29 19:12:22]

does it allow many calls to the Connect on the same instance?

[Kevin M, 2016/09/29 21:18:40]

Yes; there is no FIFO ordering constraint like there is for reads and writes.

+
+  // Returns true if the underlying transport has the necessary resources (e.g.
+  // network connectivity) to Connect() new streams.
+  virtual bool IsAvailable() = 0;
+};
+
+}  // namespace blimp
+
+#endif  // BLIMP_NET_HELIUM_HELIUM_TRANSPORT_H_