Roll src/net/third_party/quiche/src/ ad56e3f17..4de168715 (6 commits)

https://quiche.googlesource.com/quiche.git/+log/ad56e3f17dd1..4de168715fa1

$ git log ad56e3f17..4de168715 --date=short --no-merges --format='%ad %ae %s'
2020-07-16 nharper Fix use-after-free in QuicConnectionTest
2020-07-16 fayang In quic, coalesce packet of higher encryption level with initial or handshake retransmission. protected by gfe2_reloadable_flag_quic_coalesced_packet_of_higher_space.
2020-07-15 haoyuewang Support sender control of ack frequency step2: (1) add min_ack_delay transport parameters. (2) client send min_ack_delay by default. protected by gfe2_reloadable_flag_quic_record_received_min_ack_delay.
2020-07-15 renjietang Make QuicControlFrameManager talk to QuicSession via a delegate.
2020-07-15 wub Internal QUICHE change
2020-07-14 nharper Add flag count macro for quic_enable_zero_rtt_for_tls

Created with:
  roll-dep src/net/third_party/quiche/src src/third_party/quic_trace/src

Change-Id: I548d3d96b85a08bc9ee81c76090352f992685df7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2302729
Commit-Queue: Nick Harper <nharper@chromium.org>
Auto-Submit: Nick Harper <nharper@chromium.org>
Reviewed-by: David Schinazi <dschinazi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#789198}

DEPS

@@ -321,7 +321,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling feed
   # and whatever else without interference from each other.
-  'quiche_revision': 'ad56e3f17dd1b62fb3f5ff442bd2434a736fbcd7',
+  'quiche_revision': '4de168715fa1e0c5909c570c3c01a762132c94aa',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling ios_webkit
   # and whatever else without interference from each other.

net/quic/quic_flags_list.h

@@ -384,3 +384,15 @@ QUIC_FLAG(
     bool,
     FLAGS_quic_reloadable_flag_quic_bbr2_improve_adjust_network_parameters,
     false)
+
+// If true, try to coalesce packet of higher space with retransmissions to
+// mitigate RTT inflations.
+QUIC_FLAG(bool,
+          FLAGS_quic_reloadable_flag_quic_coalesced_packet_of_higher_space,
+          false)
+
+// If true, record the received min_ack_delay in transport parameters to QUIC
+// config.
+QUIC_FLAG(bool,
+          FLAGS_quic_reloadable_flag_quic_record_received_min_ack_delay,
+          false)