Enable quic_reloadable_flag_quic_avoid_leak_writer_buffer.

Change-Id: Ib6254975ed3313b1debd3e147abeec11ddfa4c0b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2292788Reviewed-by: David Schinazi <dschinazi@chromium.org>
Commit-Queue: Bin Wu <wub@chromium.org>
Cr-Commit-Position: refs/heads/master@{#788742}

net/quic/quic_flags_list.h

@@ -286,7 +286,7 @@ QUIC_FLAG(bool,
 
 // If true, QUIC will free writer-allocated packet buffer if writer->WritePacket
 // is not called.
-QUIC_FLAG(bool, FLAGS_quic_reloadable_flag_quic_avoid_leak_writer_buffer, false)
+QUIC_FLAG(bool, FLAGS_quic_reloadable_flag_quic_avoid_leak_writer_buffer, true)
 
 // If true, the B2HI connection option limits reduction of inflight_hi to
 // (1-Beta)*CWND.