Deprecate --quic_delay_sequencer_buffer_allocation_until_new_data

PiperOrigin-RevId: 438021935
diff --git a/quic/core/http/end_to_end_test.cc b/quic/core/http/end_to_end_test.cc
index b1b9b4f..03c0943 100644
--- a/quic/core/http/end_to_end_test.cc
+++ b/quic/core/http/end_to_end_test.cc
@@ -837,8 +837,6 @@
                          ::testing::PrintToStringParamName());
 
 TEST_P(EndToEndTest, HandshakeSuccessful) {
-  SetQuicReloadableFlag(quic_delay_sequencer_buffer_allocation_until_new_data,
-                        true);
   ASSERT_TRUE(Initialize());
   EXPECT_TRUE(client_->client()->WaitForOneRttKeysAvailable());
   ASSERT_TRUE(server_thread_);
diff --git a/quic/core/quic_flags_list.h b/quic/core/quic_flags_list.h
index ab6a5b3..94eb8e0 100644
--- a/quic/core/quic_flags_list.h
+++ b/quic/core/quic_flags_list.h
@@ -43,8 +43,6 @@
 QUIC_FLAG(FLAGS_quic_restart_flag_quic_default_on_pto2, true)
 // If true, default-enable 5RTO blachole detection.
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_default_enable_5rto_blackhole_detection2, true)
-// If true, delay block allocation in QuicStreamSequencerBuffer until there is actually new data available.
-QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_delay_sequencer_buffer_allocation_until_new_data, true)
 // If true, disable QUIC version Q043.
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_disable_version_q043, false)
 // If true, disable QUIC version Q046.
diff --git a/quic/core/quic_stream_sequencer_buffer.cc b/quic/core/quic_stream_sequencer_buffer.cc
index 78c55c7..a4c02f3 100644
--- a/quic/core/quic_stream_sequencer_buffer.cc
+++ b/quic/core/quic_stream_sequencer_buffer.cc
@@ -125,9 +125,6 @@
     *error_details = "Received data beyond available range.";
     return QUIC_INTERNAL_ERROR;
   }
-  if (!delay_allocation_until_new_data_) {
-    MaybeAddMoreBlocks(starting_offset + size);
-  }
 
   if (bytes_received_.Empty() ||
       starting_offset >= bytes_received_.rbegin()->max() ||
@@ -142,11 +139,7 @@
       *error_details = "Too many data intervals received for this stream.";
       return QUIC_TOO_MANY_STREAM_DATA_INTERVALS;
     }
-    if (delay_allocation_until_new_data_) {
-      QUIC_RELOADABLE_FLAG_COUNT_N(
-          quic_delay_sequencer_buffer_allocation_until_new_data, 1, 2);
-      MaybeAddMoreBlocks(starting_offset + size);
-    }
+    MaybeAddMoreBlocks(starting_offset + size);
 
     size_t bytes_copy = 0;
     if (!CopyStreamData(starting_offset, data, &bytes_copy, error_details)) {
@@ -170,11 +163,7 @@
     *error_details = "Too many data intervals received for this stream.";
     return QUIC_TOO_MANY_STREAM_DATA_INTERVALS;
   }
-  if (delay_allocation_until_new_data_) {
-    QUIC_RELOADABLE_FLAG_COUNT_N(
-        quic_delay_sequencer_buffer_allocation_until_new_data, 2, 2);
-    MaybeAddMoreBlocks(starting_offset + size);
-  }
+  MaybeAddMoreBlocks(starting_offset + size);
   for (const auto& interval : newly_received) {
     const QuicStreamOffset copy_offset = interval.min();
     const QuicByteCount copy_length = interval.max() - interval.min();
diff --git a/quic/core/quic_stream_sequencer_buffer.h b/quic/core/quic_stream_sequencer_buffer.h
index 6ea3586..18869f6 100644
--- a/quic/core/quic_stream_sequencer_buffer.h
+++ b/quic/core/quic_stream_sequencer_buffer.h
@@ -239,9 +239,6 @@
 
   // Currently received data.
   QuicIntervalSet<QuicStreamOffset> bytes_received_;
-
-  bool delay_allocation_until_new_data_ = GetQuicReloadableFlag(
-      quic_delay_sequencer_buffer_allocation_until_new_data);
 };
 
 }  // namespace quic