Don't copy the QuicAckFrame into the QuicPacketGenerator. Protected by quic_dont_copy_acks.

net/quic/quic_connection_test.cc

Index: net/quic/quic_connection_test.cc
diff --git a/net/quic/quic_connection_test.cc b/net/quic/quic_connection_test.cc
index 38ec1aa54bf1445cf91da8df7911594828927ec8..7b8314a18d3bb42f6621628a464a5f3c651dbc2e 100644
--- a/net/quic/quic_connection_test.cc
+++ b/net/quic/quic_connection_test.cc
@@ -699,7 +699,13 @@ class QuicConnectionTest : public ::testing::TestWithParam<TestParams> {
   QuicVersion version() { return GetParam().version; }
 
   QuicAckFrame* outgoing_ack() {
-    QuicConnectionPeer::PopulateAckFrame(&connection_, &ack_);
+    if (FLAGS_quic_dont_copy_acks) {
+      QuicFrame ack_frame =
+          QuicConnectionPeer::GetUpdatedAckFrame(&connection_);
+      ack_ = *ack_frame.ack_frame;
+    } else {
+      QuicConnectionPeer::PopulateAckFrame(&connection_, &ack_);
+    }
     return &ack_;
   }