Move const declarations into quic_stream_sequencer_buffer.cc

constexpr members of a class require definition in addition to declaration and initialization.
In Chromium, it is a link error:
error: undefined symbol: quic::QuicStreamSequencerBuffer::kInitialBlockCount
>>> referenced by quic_stream_sequencer_buffer.cc:88 (../../net/third_party/quiche/src/quic/core/quic_stream_sequencer_buffer.cc:88)
>>>               obj/net/third_party/quiche/quiche/quic_stream_sequencer_buffer.o:(quic::QuicStreamSequencerBuffer::MaybeAddMoreBlocks(unsigned long))
clang: error: linker command failed with exit code 1 (use -v to see invocation)

kInitialBlockCount, kBlocksGrowthFactor are only used in .cc file.

PiperOrigin-RevId: 341931802
Change-Id: Ie0dfb5d4f777bdcb68ce9cf7327d589d58dd64ff

quic/core/quic_stream_sequencer_buffer.cc

diff --git a/quic/core/quic_stream_sequencer_buffer.cc b/quic/core/quic_stream_sequencer_buffer.cc
index c4559dc..6f39938 100644
--- a/quic/core/quic_stream_sequencer_buffer.cc
+++ b/quic/core/quic_stream_sequencer_buffer.cc
@@ -31,6 +31,13 @@
 // arrives.
 const size_t kMaxNumDataIntervalsAllowed = 2 * kMaxPacketGap;
 
+// Number of blocks allocated initially.
+constexpr size_t kInitialBlockCount = 8u;
+
+// How fast block pointers container grow in size.
+// Choose 4 to reduce the amount of reallocation.
+constexpr int kBlocksGrowthFactor = 4;
+
 }  // namespace
 
 QuicStreamSequencerBuffer::QuicStreamSequencerBuffer(size_t max_capacity_bytes)

quic/core/quic_stream_sequencer_buffer.h

diff --git a/quic/core/quic_stream_sequencer_buffer.h b/quic/core/quic_stream_sequencer_buffer.h
index 66acc53..674e3d9 100644
--- a/quic/core/quic_stream_sequencer_buffer.h
+++ b/quic/core/quic_stream_sequencer_buffer.h
@@ -82,14 +82,7 @@
   // Size of blocks used by this buffer.
   // Choose 8K to make block large enough to hold multiple frames, each of
   // which could be up to 1.5 KB.
-  static constexpr size_t kBlockSizeBytes = 8 * 1024;  // 8KB
-
-  // Number of blocks allocated initially.
-  static constexpr size_t kInitialBlockCount = 8u;
-
-  // How fast block pointers container grow in size.
-  // Choose 4 to reduce the amount of reallocation.
-  static constexpr int kBlocksGrowthFactor = 4;
+  static const size_t kBlockSizeBytes = 8 * 1024;  // 8KB
 
   // The basic storage block used by this buffer.
   struct QUIC_EXPORT_PRIVATE BufferBlock {