Blimp: Add BlobChannelReceiver and bindings interface.

blimp/net/blob_channel/blob_channel_bindings.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_BLOB_CHANNEL_BINDINGS_H_
 #define BLIMP_NET_BLOB_CHANNEL_BLOB_CHANNEL_BINDINGS_H_
 
+#include <memory>
 #include <string>
 #include <vector>
 
 namespace blimp {
 
 // Interfaces for attaching transport-specific implementations to BlobChannel
 // operations. The caller is responsible for handling call deduplication;
 // bindings objects simply execute the command.
 
 class BlobSenderBindings {
  public:
   // Send blob |id| with payload |data| to the receiver.
   virtual void Send(const std::string& id,
                     const std::vector<uint8_t>& data) = 0;
 };
 
+class BlobReceiverBindings {
+ public:
+  class Delegate {

[Wez, 2016/04/15 17:27:43]

Why is this callback wrapped in a class and called a delegate, while the
BlobChannelReceiver just has a callback?

[Kevin M, 2016/04/15 23:53:43]

The delegate dispatches events for a single client; the BlobChannelReceiver
needs to fan out events to >1 clients (multiple frames can request the same blob
concurrently).

+   public:
+    // Invoked when a blob arrives asynchronously.
+    virtual void OnBlobReceived(const std::string& id,
+                                std::unique_ptr<std::vector<uint8_t>> data) = 0;
+  };
+
+  // Requests the blob |id| from the sender. The delegate method
+  // OnBlobReceived() is triggered if and when the blob arrives.
+  virtual void Get(const std::string& id) = 0;
+
+  virtual void SetDelegate(Delegate* delegate) = 0;
+};
+
 }  // namespace blimp
 
 #endif  // BLIMP_NET_BLOB_CHANNEL_BLOB_CHANNEL_BINDINGS_H_