Use ConnectionErrorObserver, not callbacks, for error handling.

blimp/net/blimp_connection.cc

Index: blimp/net/blimp_connection.cc
diff --git a/blimp/net/blimp_connection.cc b/blimp/net/blimp_connection.cc
index 4b48f773d488d97ecd85b3a0673b198ffc5260bf..3d8676a934a5bf019c0526203107afa3be54d287 100644
--- a/blimp/net/blimp_connection.cc
+++ b/blimp/net/blimp_connection.cc
@@ -91,10 +91,13 @@ void BlimpMessageSender::ProcessMessage(
 void BlimpMessageSender::OnWritePacketComplete(int result) {
   DVLOG(2) << "OnWritePacketComplete, result=" << result;
   DCHECK_NE(net::ERR_IO_PENDING, result);
-  base::ResetAndReturn(&pending_process_msg_callback_).Run(result);
+
   if (result != net::OK) {
     error_observer_->OnConnectionError(result);
+    return;
   }
+
+  base::ResetAndReturn(&pending_process_msg_callback_).Run(result);

[haibinlu, 2016/05/03 21:23:05]

nit. use net::OK instead to be specific.

Also, add comment about when callers can expect callback to always have net::OK.

[Kevin M, 2016/05/24 20:47:04]

Done.

 }
 
 }  // namespace
@@ -103,16 +106,16 @@ BlimpConnection::BlimpConnection(std::unique_ptr<PacketReader> reader,
                                  std::unique_ptr<PacketWriter> writer)
     : reader_(std::move(reader)),
       message_pump_(new BlimpMessagePump(reader_.get())),
-      writer_(std::move(writer)),
-      outgoing_msg_processor_(new BlimpMessageSender(writer_.get())) {
+      writer_(std::move(writer)) {
   DCHECK(writer_);
+  DCHECK(reader_);
 
-  // Observe the connection errors received by any of this connection's network
-  // objects.
   message_pump_->set_error_observer(this);
-  BlimpMessageSender* sender =
-      static_cast<BlimpMessageSender*>(outgoing_msg_processor_.get());
+
+  std::unique_ptr<BlimpMessageSender> sender(
+      new BlimpMessageSender(writer_.get()));
   sender->set_error_observer(this);
+  outgoing_msg_processor_ = std::move(sender);
 }
 
 BlimpConnection::BlimpConnection() {}