Deprecate gfe2_flags_reloadable_quic_connection_uses_abstract_connection_id_generator.

Also deletes legacy connection ID update code.

PiperOrigin-RevId: 481936199
diff --git a/quiche/quic/core/quic_connection_test.cc b/quiche/quic/core/quic_connection_test.cc
index ee2a090..3a4e7a9 100644
--- a/quiche/quic/core/quic_connection_test.cc
+++ b/quiche/quic/core/quic_connection_test.cc
@@ -1877,9 +1877,7 @@
   QuicConnectionPeer::SetAddressValidated(&connection_);
 
   // Sends new server CID to client.
-  if (GetQuicReloadableFlag(
-          quic_connection_uses_abstract_connection_id_generator) &&
-      !connection_.connection_id().IsEmpty()) {
+  if (!connection_.connection_id().IsEmpty()) {
     EXPECT_CALL(connection_id_generator_, GenerateNextConnectionId(_))
         .WillOnce(Return(TestConnectionId(456)));
   }
@@ -2082,9 +2080,7 @@
 
   // Sends new server CID to client.
   QuicConnectionId new_cid;
-  if (GetQuicReloadableFlag(
-          quic_connection_uses_abstract_connection_id_generator) &&
-      !connection_.connection_id().IsEmpty()) {
+  if (!connection_.connection_id().IsEmpty()) {
     EXPECT_CALL(connection_id_generator_, GenerateNextConnectionId(_))
         .WillOnce(Return(TestConnectionId(456)));
   }
@@ -2146,9 +2142,7 @@
 
   // Sends new server CID to client.
   QuicConnectionId new_cid;
-  if (GetQuicReloadableFlag(
-          quic_connection_uses_abstract_connection_id_generator) &&
-      !connection_.connection_id().IsEmpty()) {
+  if (!connection_.connection_id().IsEmpty()) {
     EXPECT_CALL(connection_id_generator_, GenerateNextConnectionId(_))
         .WillOnce(Return(TestConnectionId(456)));
   }
@@ -2220,9 +2214,7 @@
   QuicConnectionId server_cid0 = connection_.connection_id();
   QuicConnectionId server_cid1;
   // Sends new server CID to client.
-  if (GetQuicReloadableFlag(
-          quic_connection_uses_abstract_connection_id_generator) &&
-      !connection_.connection_id().IsEmpty()) {
+  if (!connection_.connection_id().IsEmpty()) {
     EXPECT_CALL(connection_id_generator_, GenerateNextConnectionId(_))
         .WillOnce(Return(TestConnectionId(456)));
   }
@@ -13304,9 +13296,7 @@
   QuicConnectionId client_cid1 = TestConnectionId(2);
   QuicConnectionId server_cid1;
   // Sends new server CID to client.
-  if (GetQuicReloadableFlag(
-          quic_connection_uses_abstract_connection_id_generator) &&
-      !connection_.connection_id().IsEmpty()) {
+  if (!connection_.connection_id().IsEmpty()) {
     EXPECT_CALL(connection_id_generator_, GenerateNextConnectionId(_))
         .WillOnce(Return(TestConnectionId(456)));
   }
@@ -13458,9 +13448,7 @@
   QuicConnectionId server_cid0 = connection_.connection_id();
   QuicConnectionId server_cid1;
   // Sends new server CID to client.
-  if (GetQuicReloadableFlag(
-          quic_connection_uses_abstract_connection_id_generator) &&
-      !connection_.connection_id().IsEmpty()) {
+  if (!connection_.connection_id().IsEmpty()) {
     EXPECT_CALL(connection_id_generator_, GenerateNextConnectionId(_))
         .WillOnce(Return(TestConnectionId(456)));
   }
@@ -13585,9 +13573,7 @@
   QuicConnectionId client_cid1 = TestConnectionId(2);
   QuicConnectionId server_cid1;
   // Sends new server CID to client.
-  if (GetQuicReloadableFlag(
-          quic_connection_uses_abstract_connection_id_generator) &&
-      !connection_.connection_id().IsEmpty()) {
+  if (!connection_.connection_id().IsEmpty()) {
     EXPECT_CALL(connection_id_generator_, GenerateNextConnectionId(_))
         .WillOnce(Return(TestConnectionId(456)));
   }
@@ -13699,9 +13685,7 @@
   QuicConnectionId client_cid1 = TestConnectionId(2);
   QuicConnectionId server_cid1;
   // Sends new server CID to client.
-  if (GetQuicReloadableFlag(
-          quic_connection_uses_abstract_connection_id_generator) &&
-      !connection_.connection_id().IsEmpty()) {
+  if (!connection_.connection_id().IsEmpty()) {
     EXPECT_CALL(connection_id_generator_, GenerateNextConnectionId(_))
         .WillOnce(Return(TestConnectionId(456)));
   }
@@ -13838,11 +13822,8 @@
   ASSERT_EQ(packet_creator->GetDestinationConnectionId(), server_cid0);
 
   // Client will issue a new client connection ID to server.
-  if (GetQuicReloadableFlag(
-          quic_connection_uses_abstract_connection_id_generator)) {
-    EXPECT_CALL(connection_id_generator_, GenerateNextConnectionId(_))
-        .WillOnce(Return(TestConnectionId(456)));
-  }
+  EXPECT_CALL(connection_id_generator_, GenerateNextConnectionId(_))
+      .WillOnce(Return(TestConnectionId(456)));
   EXPECT_CALL(visitor_, SendNewConnectionId(_))
       .WillOnce(Invoke([&](const QuicNewConnectionIdFrame& frame) {
         client_cid1 = frame.connection_id;
@@ -14001,11 +13982,8 @@
 
   // Client will issue a new client connection ID to server.
   QuicConnectionId new_client_connection_id;
-  if (GetQuicReloadableFlag(
-          quic_connection_uses_abstract_connection_id_generator)) {
-    EXPECT_CALL(connection_id_generator_, GenerateNextConnectionId(_))
-        .WillOnce(Return(TestConnectionId(456)));
-  }
+  EXPECT_CALL(connection_id_generator_, GenerateNextConnectionId(_))
+      .WillOnce(Return(TestConnectionId(456)));
   EXPECT_CALL(visitor_, SendNewConnectionId(_))
       .WillOnce(Invoke([&](const QuicNewConnectionIdFrame& frame) {
         new_client_connection_id = frame.connection_id;
@@ -14259,9 +14237,7 @@
   set_perspective(Perspective::IS_SERVER);
   connection_.CreateConnectionIdManager();
 
-  if (GetQuicReloadableFlag(
-          quic_connection_uses_abstract_connection_id_generator) &&
-      !connection_.connection_id().IsEmpty()) {
+  if (!connection_.connection_id().IsEmpty()) {
     EXPECT_CALL(connection_id_generator_, GenerateNextConnectionId(_))
         .WillOnce(Return(TestConnectionId(456)));
   }
@@ -14298,9 +14274,7 @@
   QuicRetireConnectionIdFrame frame;
   frame.sequence_number = 0u;
   if (connection_.connection_migration_use_new_cid()) {
-    if (GetQuicReloadableFlag(
-            quic_connection_uses_abstract_connection_id_generator) &&
-        !connection_.connection_id().IsEmpty()) {
+    if (!connection_.connection_id().IsEmpty()) {
       EXPECT_CALL(connection_id_generator_, GenerateNextConnectionId(cid0))
           .WillOnce(Return(TestConnectionId(456)));
       EXPECT_CALL(connection_id_generator_,
@@ -14340,9 +14314,7 @@
   EXPECT_EQ(connection_.GetOneActiveServerConnectionId(), cid0);
 
   connection_.SetDefaultEncryptionLevel(ENCRYPTION_FORWARD_SECURE);
-  if (GetQuicReloadableFlag(
-          quic_connection_uses_abstract_connection_id_generator) &&
-      !connection_.connection_id().IsEmpty()) {
+  if (!connection_.connection_id().IsEmpty()) {
     EXPECT_CALL(connection_id_generator_, GenerateNextConnectionId(_))
         .WillOnce(Return(TestConnectionId(456)));
   }
@@ -14377,9 +14349,7 @@
 
   // Packet2 with RetireConnectionId frame trigers sending NewConnectionId
   // immediately.
-  if (GetQuicReloadableFlag(
-          quic_connection_uses_abstract_connection_id_generator) &&
-      !connection_.connection_id().IsEmpty()) {
+  if (!connection_.connection_id().IsEmpty()) {
     EXPECT_CALL(connection_id_generator_, GenerateNextConnectionId(_))
         .WillOnce(Return(TestConnectionId(456)));
   }
@@ -14793,15 +14763,12 @@
       !connection_.connection_migration_use_new_cid()) {
     return;
   }
-  if (GetQuicReloadableFlag(
-          quic_connection_uses_abstract_connection_id_generator)) {
-    EXPECT_CALL(connection_id_generator_,
-                GenerateNextConnectionId(TestConnectionId(12)))
-        .WillOnce(Return(TestConnectionId(456)));
-    EXPECT_CALL(connection_id_generator_,
-                GenerateNextConnectionId(TestConnectionId(456)))
-        .WillOnce(Return(TestConnectionId(789)));
-  }
+  EXPECT_CALL(connection_id_generator_,
+              GenerateNextConnectionId(TestConnectionId(12)))
+      .WillOnce(Return(TestConnectionId(456)));
+  EXPECT_CALL(connection_id_generator_,
+              GenerateNextConnectionId(TestConnectionId(456)))
+      .WillOnce(Return(TestConnectionId(789)));
   EXPECT_CALL(visitor_, SendNewConnectionId(_)).Times(2);
   EXPECT_CALL(visitor_, OnRstStream(_));
   EXPECT_CALL(visitor_, OnWindowUpdateFrame(_));