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 e8f3c68cc376131814ccd41bcf308c8950a2ce91..7b74c0a245d9d21f368c8b32d683905aec8db04c 100644
--- a/blimp/net/blimp_connection.cc
+++ b/blimp/net/blimp_connection.cc
@@ -20,7 +20,6 @@
 #include "net/base/completion_callback.h"
 
 namespace blimp {
-namespace {
 
 // Forwards incoming blimp messages to PacketWriter.
 class BlimpMessageSender : public BlimpMessageProcessor {
@@ -33,6 +32,8 @@ class BlimpMessageSender : public BlimpMessageProcessor {
   }
 
   // BlimpMessageProcessor implementation.
+  // |callback| receives net::OK on write success, or receives an error code
+  // otherwise.
   void ProcessMessage(std::unique_ptr<BlimpMessage> message,
                       const net::CompletionCallback& callback) override;
 
@@ -91,28 +92,33 @@ 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);
+
+  // Create a stack-local copy of |pending_process_msg_callback_|, in case an
+  // observer deletes |this|.
+  net::CompletionCallback process_callback =
+      base::ResetAndReturn(&pending_process_msg_callback_);
+
   if (result != net::OK) {
     error_observer_->OnConnectionError(result);
   }
-}
 
-}  // namespace
+  process_callback.Run(net::OK);
+}
 
 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() {}