Deprecate --gfe2_reloadable_flag_quic_do_not_evict_unacked_entry.

See https://crbug.com/1441880.

PiperOrigin-RevId: 543452125
diff --git a/quiche/quic/core/qpack/qpack_encoder.cc b/quiche/quic/core/qpack/qpack_encoder.cc
index 7ac9519..9ee5226 100644
--- a/quiche/quic/core/qpack/qpack_encoder.cc
+++ b/quiche/quic/core/qpack/qpack_encoder.cc
@@ -93,16 +93,11 @@
       blocking_manager_.known_received_count();
 
   // The index of the oldest entry that must not be evicted. Blocking entries
-  // must not be evicted.
-  uint64_t smallest_non_evictable_index =
-      blocking_manager_.smallest_blocking_index();
-  // Additionally, unacknowledged entries must not be evicted, even if they have
-  // no outstanding references (see https://crbug.com/1441880 for more context).
-  if (GetQuicReloadableFlag(quic_do_not_evict_unacked_entry)) {
-    QUIC_RELOADABLE_FLAG_COUNT(quic_do_not_evict_unacked_entry);
-    smallest_non_evictable_index =
-        std::min(smallest_non_evictable_index, known_received_count);
-  }
+  // must not be evicted. Also, unacknowledged entries must not be evicted,
+  // even if they have no outstanding references (see https://crbug.com/1441880
+  // for more context).
+  uint64_t smallest_non_evictable_index = std::min(
+      blocking_manager_.smallest_blocking_index(), known_received_count);
 
   // Only entries with index greater than or equal to |draining_index| are
   // allowed to be referenced.
diff --git a/quiche/quic/core/qpack/qpack_encoder_test.cc b/quiche/quic/core/qpack/qpack_encoder_test.cc
index 0e59048..03d7a3f 100644
--- a/quiche/quic/core/qpack/qpack_encoder_test.cc
+++ b/quiche/quic/core/qpack/qpack_encoder_test.cc
@@ -675,33 +675,14 @@
   spdy::Http2HeaderBlock header_list2;
   header_list2["bar"] = "baz";
 
-  if (GetQuicReloadableFlag(quic_do_not_evict_unacked_entry)) {
-    EXPECT_EQ(absl::HexStringToBytes("0000"        // prefix
-                                     "23626172"    // literal name "bar"
-                                     "0362617a"),  // literal value "baz"
-              encoder_.EncodeHeaderList(/* stream_id = */ 2, header_list2,
-                                        &encoder_stream_sent_byte_count_));
+  EXPECT_EQ(absl::HexStringToBytes("0000"        // prefix
+                                   "23626172"    // literal name "bar"
+                                   "0362617a"),  // literal value "baz"
+            encoder_.EncodeHeaderList(/* stream_id = */ 2, header_list2,
+                                      &encoder_stream_sent_byte_count_));
 
-    EXPECT_EQ(1u, header_table->inserted_entry_count());
-    EXPECT_EQ(0u, header_table->dropped_entry_count());
-  } else {
-    // Insert one entry into the dynamic table, evicting the first entry.
-    std::string insert_entries2 = absl::HexStringToBytes(
-        "43"          // insert without name reference
-        "626172"      // name "bar"
-        "0362617a");  // value "baz"
-    EXPECT_CALL(encoder_stream_sender_delegate_,
-                WriteStreamData(Eq(insert_entries2)));
-
-    EXPECT_EQ(
-        absl::HexStringToBytes("0100"  // prefix
-                               "80"),  // dynamic entry with relative index 0
-        encoder_.EncodeHeaderList(/* stream_id = */ 2, header_list2,
-                                  &encoder_stream_sent_byte_count_));
-
-    EXPECT_EQ(2u, header_table->inserted_entry_count());
-    EXPECT_EQ(1u, header_table->dropped_entry_count());
-  }
+  EXPECT_EQ(1u, header_table->inserted_entry_count());
+  EXPECT_EQ(0u, header_table->dropped_entry_count());
 }
 
 }  // namespace
diff --git a/quiche/quic/core/quic_flags_list.h b/quiche/quic/core/quic_flags_list.h
index 778269f..857fea7 100644
--- a/quiche/quic/core/quic_flags_list.h
+++ b/quiche/quic/core/quic_flags_list.h
@@ -73,8 +73,6 @@
 QUIC_FLAG(quic_restart_flag_quic_enable_sending_bandwidth_estimate_when_network_idle_v2, true)
 // If true, set burst token to 2 in cwnd bootstrapping experiment.
 QUIC_FLAG(quic_reloadable_flag_quic_conservative_bursts, false)
-// If true, unacked QPACK entries with no references will not be evicted.
-QUIC_FLAG(quic_reloadable_flag_quic_do_not_evict_unacked_entry, true)
 // If true, use BBRv2 as the default congestion controller. Takes precedence over --quic_default_to_bbr.
 QUIC_FLAG(quic_reloadable_flag_quic_default_to_bbr_v2, false)
 // If true, use a LRU cache to record client addresses of packets received on server\'s original address.