Host extensions

remoting/host/extension.h

Index: remoting/host/extension.h
diff --git a/remoting/host/extension.h b/remoting/host/extension.h
new file mode 100644
index 0000000000000000000000000000000000000000..e3e85817ccec973ea36b1f3b70be7a95979ee40c
--- /dev/null
+++ b/remoting/host/extension.h
@@ -0,0 +1,38 @@
+// Copyright 2014 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 REMOTING_HOST_EXTENSION_H_
+#define REMOTING_HOST_EXTENSION_H_
+
+#include <string>
+
+#include "base/memory/scoped_ptr.h"
+
+namespace remoting {

[Wez, 2014/05/28 01:05:59]

Should this belong under remoting::protocol, since it's protocol-specific?

[dcaiafa, 2014/05/28 22:44:58]

Per our offline conversation: it should be under remoting only because there is
no client analog (except in javascript).

+
+class ClientSession;
+class ExtensionSession;
+
+// Extends |ChromotingHost| with new functionality, and can use extension
+// messages to communicate with the client.
+class Extension {

[Wez, 2014/05/28 01:05:59]

Since this is in the remoting namespace, but host-specific, should it be
HostExtension?

[dcaiafa, 2014/05/28 22:44:58]

Done.

+ public:
+  // Returns a space-separated list of capabilities provided by this extension.
+  // Capabilities are used to inform the client of the availability of an
+  // extension.

[Wez, 2014/05/28 01:05:59]

How? Are they e.g. merged into the capabilities the host reports to the client
at startup?

[dcaiafa, 2014/05/28 22:44:58]

Done.

+  virtual std::string GetCapabilities() = 0;
+
+  // Creates an extension session, which can handle extension messages for a
+  // client session.
+  // It may return NULL.

[Wez, 2014/05/28 01:05:59]

Why would it do that? What happens if it does? Suggest e.g. "If NULL is returned
then the extension will not be available to the client session."

[dcaiafa, 2014/05/28 22:44:58]

Done.

+  // |client_session| must outlive the resulting |ExtensionSession|.
+  virtual scoped_ptr<ExtensionSession> CreateExtensionSession(
+      ClientSession* client_session) = 0;

[Wez, 2014/05/28 01:05:59]

Why do we need to pass the ClientSession in here?

[dcaiafa, 2014/05/28 22:44:58]

So the extension can (among others):
- Query client capabilities
- Send extension messages
- Disconnect session on error

+};
+
+typedef std::vector<Extension*> ExtensionList;
+
+}  // namespace remoting
+
+#endif  // REMOTING_HOST_EXTENSION_H_