Introduces ability for session to wait on a migration trigger for a new

net/quic/chromium/quic_chromium_packet_writer.cc

Index: net/quic/chromium/quic_chromium_packet_writer.cc
diff --git a/net/quic/chromium/quic_chromium_packet_writer.cc b/net/quic/chromium/quic_chromium_packet_writer.cc
index 5478d7173c88c23c89af76e315d27a32e19b6ba5..795a9327c4142e81780c7586500bfa34b3e2de08 100644
--- a/net/quic/chromium/quic_chromium_packet_writer.cc
+++ b/net/quic/chromium/quic_chromium_packet_writer.cc
@@ -46,6 +46,7 @@ WriteResult QuicChromiumPacketWriter::WritePacketToSocket(
                           base::Bind(&QuicChromiumPacketWriter::OnWriteComplete,
                                      weak_factory_.GetWeakPtr()));
 
+  DLOG(INFO) << "socket returned: " << rv;
   if (rv < 0 && rv != ERR_IO_PENDING && delegate_ != nullptr) {
     // If write error, then call delegate's HandleWriteError, which
     // may be able to migrate and rewrite packet on a new socket.
@@ -59,6 +60,7 @@ WriteResult QuicChromiumPacketWriter::WritePacketToSocket(
       UMA_HISTOGRAM_SPARSE_SLOWLY("Net.QuicSession.WriteError", -rv);
       status = WRITE_STATUS_ERROR;
     } else {
+      DLOG(INFO) << "***async completion.";
       status = WRITE_STATUS_BLOCKED;
       write_blocked_ = true;
       packet_ = packet;
@@ -93,6 +95,7 @@ void QuicChromiumPacketWriter::OnWriteComplete(int rv) {
   DCHECK_NE(rv, ERR_IO_PENDING);
   DCHECK(delegate_) << "Uninitialized delegate.";
   write_blocked_ = false;
+  DLOG(INFO) << "Write completed asynchronously: " << rv;
   if (rv < 0) {
     // If write error, then call delegate's HandleWriteError, which
     // may be able to migrate and rewrite packet on a new socket.