Make PacketReader/PacketWriter interfaces async-only.

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 e7db062b8e9bf8814bbc7f58f64a7e3cce4e120e..df54406b3fabd840bd87a2e3bd3c266a61983b5d 100644
--- a/blimp/net/blimp_connection.cc
+++ b/blimp/net/blimp_connection.cc
@@ -75,11 +75,7 @@ void BlimpMessageSender::ProcessMessage(
   write_packet_callback_.Reset(base::Bind(
       &BlimpMessageSender::OnWritePacketComplete, base::Unretained(this)));
   pending_process_msg_callback_ = callback;
-  int result = writer_->WritePacket(buffer_, write_packet_callback_.callback());
-  if (result != net::ERR_IO_PENDING) {
-    base::MessageLoop::current()->PostTask(
-        FROM_HERE, base::Bind(write_packet_callback_.callback(), result));
-  }
+  writer_->WritePacket(buffer_, write_packet_callback_.callback());
 }
 
 void BlimpMessageSender::OnWritePacketComplete(int result) {