Blimp: Add BlobChannel Helium messages and delegate impls.

blimp/net/blob_channel/helium_blob_receiver_delegate.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_BLOB_CHANNEL_HELIUM_BLOB_RECEIVER_DELEGATE_H_
+#define BLIMP_NET_BLOB_CHANNEL_HELIUM_BLOB_RECEIVER_DELEGATE_H_
+
+#include <memory>
+
+#include "blimp/net/blimp_message_processor.h"
+#include "blimp/net/blimp_net_export.h"
+#include "blimp/net/blob_channel/blob_channel_receiver.h"
+#include "net/base/completion_callback.h"
+
+namespace blimp {
+
+// Receives and processes incoming blob messages in BlimpMessage format and
+// passes them to an attached BlobChannelReceiver.

[Wez, 2016/05/24 01:18:40]

It's still not clear how the BlobChannelReceiver becomes attached; this comment
needs to explain that the caller must call
BlobChannelReceiver::Delegate::SetReceiver() on this object before handing it
messages to process.

[Kevin M, 2016/05/25 00:06:33]

Done.

+class BLIMP_NET_EXPORT HeliumBlobReceiverDelegate
+    : public BlobChannelReceiver::Delegate,
+      public BlimpMessageProcessor {
+ public:
+  HeliumBlobReceiverDelegate();
+  ~HeliumBlobReceiverDelegate() override;
+
+ private:
+  // BlimpMessageProcessor implementation.
+  void ProcessMessage(std::unique_ptr<BlimpMessage> message,
+                      const net::CompletionCallback& callback) override;
+
+  DISALLOW_COPY_AND_ASSIGN(HeliumBlobReceiverDelegate);
+};
+
+}  // namespace blimp
+
+#endif  // BLIMP_NET_BLOB_CHANNEL_HELIUM_BLOB_RECEIVER_DELEGATE_H_