Add interfaces for most major Blimp net components.

blimp/net/blimp_message_processor.h

Index: blimp/net/blimp_message_processor.h
diff --git a/blimp/net/blimp_message_processor.h b/blimp/net/blimp_message_processor.h
new file mode 100644
index 0000000000000000000000000000000000000000..b3e0ac2af2fba80a499436ac3eca824bdccab28b
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+++ b/blimp/net/blimp_message_processor.h
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+// Copyright 2015 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_BLIMP_MESSAGE_PROCESSOR_H_
+#define BLIMP_NET_BLIMP_MESSAGE_PROCESSOR_H_
+
+#include "net/base/completion_callback.h"
+
+namespace blimp {
+
+class BlimpMessage;
+
+// Interface implemented by components that process BlimpMessages.
+// Message processing workflows can be created as a filter chain of
+// BlimpMessageProcessors, and test processors can be added to validate portions
+// of the filter chain in isolation.
+class BlimpMessageProcessor {
+ public:
+  virtual ~BlimpMessageProcessor() {}
+
+  // Processes the BlimpMessage asynchronously.
+  // The result of the operation is returned to the caller via |callback|.
+  virtual void ProcessMessage(const BlimpMessage& message,
+                              const net::CompletionCallback& callback) = 0;
+};
+
+}  // namespace blimp
+
+#endif  // BLIMP_NET_BLIMP_MESSAGE_PROCESSOR_H_