Remove the previous headers_stream_ and Change unowned_headers_stream_ to header_stream_.

The unique_ptr headers_stream is now only used as a temporary variable to pass into stream_map. No need to have it as a member variable anymore.

gfe-relnote: No behavior change. Not protected.
PiperOrigin-RevId: 258403361
Change-Id: Idefbab511707878e6904c58f0aaef7c4f205f710
diff --git a/quic/core/http/quic_spdy_session.cc b/quic/core/http/quic_spdy_session.cc
index 3fe1f5c..367a99b 100644
--- a/quic/core/http/quic_spdy_session.cc
+++ b/quic/core/http/quic_spdy_session.cc
@@ -375,12 +375,12 @@
         kDefaultQpackMaxDynamicTableCapacity);
   }
 
-  headers_stream_ = QuicMakeUnique<QuicHeadersStream>((this));
+  auto headers_stream = QuicMakeUnique<QuicHeadersStream>((this));
   DCHECK_EQ(QuicUtils::GetHeadersStreamId(connection()->transport_version()),
-            headers_stream_->id());
+            headers_stream->id());
 
-  unowned_headers_stream_ = headers_stream_.get();
-  RegisterStaticStream(std::move(headers_stream_),
+  headers_stream_ = headers_stream.get();
+  RegisterStaticStream(std::move(headers_stream),
                        /*stream_already_counted = */ false);
 
   if (VersionHasStreamType(connection()->transport_version())) {