Blimp: Add BlobChannel Helium messages and delegate impls.

blimp/net/blob_channel/helium_blob_receiver_delegate.cc

+// 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.
+
+#include "blimp/net/blob_channel/helium_blob_receiver_delegate.h"
+
+#include "blimp/common/blob_cache/blob_cache.h"
+#include "blimp/common/proto/blimp_message.pb.h"
+#include "blimp/common/proto/blob_channel.pb.h"
+#include "net/base/net_errors.h"
+
+namespace blimp {
+
+HeliumBlobReceiverDelegate::HeliumBlobReceiverDelegate() {}
+
+HeliumBlobReceiverDelegate::~HeliumBlobReceiverDelegate() {}
+
+void HeliumBlobReceiverDelegate::ProcessMessage(
+    std::unique_ptr<BlimpMessage> message,
+    const net::CompletionCallback& callback) {
+  if (!message->has_blob_channel()) {
+    DLOG(WARNING) << "BlobChannel message has no |blob_channel| submessage.";
+    callback.Run(net::ERR_INVALID_ARGUMENT);
+    return;
+  }
+
+  BlobChannelMessage* blob_msg = message->mutable_blob_channel();

[Wez, 2016/05/20 21:46:18]

nit: Comment here to explain why you take a mutable pointer to the channel
message.

[Kevin M, 2016/05/23 20:48:07]

Done.

+  if (blob_msg->type() != BlobChannelMessage::TRANSFER_BLOB) {
+    callback.Run(net::ERR_NOT_IMPLEMENTED);
+    return;
+  }
+
+  if (blob_msg->blob_id().empty()) {
+    callback.Run(net::ERR_INVALID_ARGUMENT);
+    return;
+  }
+
+  // Create a temporarily non-const BlobData so that we may efficiently reuse
+  // the allocated payload string via string::swap().
+  //
+  // BlobData becomes const once it is implicitly cast to a BlobDataPtr
+  // during the call to OnBlobReceived().

[Wez, 2016/05/20 21:46:18]

I think the point here is that we don't store it to a BlobDataPtr because that
marks the BlobData as const?

[Kevin M, 2016/05/23 20:48:07]

Done.

+  scoped_refptr<BlobData> blob_data(new BlobData);
+  blob_data->data.swap(*blob_msg->mutable_payload());
+  OnBlobReceived(blob_msg->blob_id(), blob_data);
+
+  callback.Run(net::OK);
+}
+
+}  // namespace blimp