Move QuicIoVector into its own header file. No behavior change.

net/quic/core/quic_protocol.h

Index: net/quic/core/quic_protocol.h
diff --git a/net/quic/core/quic_protocol.h b/net/quic/core/quic_protocol.h
index 69bc7f166cf958e3eaac5f332e133e45ba3ac98f..7ebff6b3436a400e4dc2064b02e17422df9171b2 100644
--- a/net/quic/core/quic_protocol.h
+++ b/net/quic/core/quic_protocol.h
@@ -764,17 +764,6 @@ struct PendingRetransmission {
   QuicPacketNumberLength packet_number_length;
 };
 
-// Convenience wrapper to wrap an iovec array and the total length, which must
-// be less than or equal to the actual total length of the iovecs.
-struct NET_EXPORT_PRIVATE QuicIOVector {
-  QuicIOVector(const struct iovec* iov, int iov_count, size_t total_length)
-      : iov(iov), iov_count(iov_count), total_length(total_length) {}
-
-  const struct iovec* iov;
-  const int iov_count;
-  const size_t total_length;
-};
-
 }  // namespace net
 
 #endif  // NET_QUIC_QUIC_PROTOCOL_H_