Blimp: Add BlobChannel Helium messages and delegate impls.

blimp/net/blob_channel/blob_channel_receiver.h

Index: blimp/net/blob_channel/blob_channel_receiver.h
diff --git a/blimp/net/blob_channel/blob_channel_receiver.h b/blimp/net/blob_channel/blob_channel_receiver.h
index bdfcd236bd62e5a58da2c0d41f1fe0cc1592b75e..390058c426a825698affd182203e591c265fd225 100644
--- a/blimp/net/blob_channel/blob_channel_receiver.h
+++ b/blimp/net/blob_channel/blob_channel_receiver.h
@@ -16,7 +16,6 @@ namespace blimp {
 
 class BlobCache;
 
-// Receives blobs from a remote sender.
 class BLIMP_NET_EXPORT BlobChannelReceiver {
  public:
   class Delegate {

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

Re-reviewing the HeliumBlobReceiverDelegate I was finding this Delegate
arrangement very strange.

The Delegate as you have it here is really a base implementation of a delegate,
and all that it actually does is accept the BlobChannelReceiver and store it, so
the subclass can call OnBlobReceived.

It would be cleaner to have this be a pure interface and let
HeliumBlobReceiverDelegate store the receiver and call it, I think.

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

Done.

@@ -24,44 +23,34 @@ class BLIMP_NET_EXPORT BlobChannelReceiver {
     Delegate();
     virtual ~Delegate();
 
+    // Sets the Receiver object which will take incoming blobs.
+    void SetReceiver(BlobChannelReceiver* receiver);
+
    protected:
     // Forwards incoming blob data to |receiver_|.
     void OnBlobReceived(const BlobId& id, BlobDataPtr data);
 
    private:
-    friend class BlobChannelReceiver;
-
-    // Sets the Receiver object which will take incoming blobs.
-    void SetReceiver(BlobChannelReceiver* receiver);
-
     BlobChannelReceiver* receiver_ = nullptr;
 
     DISALLOW_COPY_AND_ASSIGN(Delegate);
   };
 
-  BlobChannelReceiver(std::unique_ptr<BlobCache> cache,
-                      std::unique_ptr<Delegate> delegate);
-  ~BlobChannelReceiver();
+  virtual ~BlobChannelReceiver() {}
+
+  // Constructs a BlobChannelReceiverImpl object for use.
+  static std::unique_ptr<BlobChannelReceiver> Create(
+      std::unique_ptr<BlobCache> cache,
+      std::unique_ptr<Delegate> delegate);
 
   // Gets a blob from the BlobChannel.
   // Returns nullptr if the blob is not available in the channel.
   // Can be accessed concurrently from any thread. Calling code must ensure that
   // the object instance outlives all calls to Get().
-  BlobDataPtr Get(const BlobId& id);
-
- private:
-  friend class Delegate;
+  virtual BlobDataPtr Get(const BlobId& id) = 0;
 
   // Called by Delegate::OnBlobReceived() when a blob arrives over the channel.
-  void OnBlobReceived(const BlobId& id, BlobDataPtr data);
-
-  std::unique_ptr<BlobCache> cache_;
-  std::unique_ptr<Delegate> delegate_;
-
-  // Guards against concurrent access to |cache_|.
-  base::Lock cache_lock_;
-
-  DISALLOW_COPY_AND_ASSIGN(BlobChannelReceiver);
+  virtual void OnBlobReceived(const BlobId& id, BlobDataPtr data) = 0;
 };
 
 }  // namespace blimp