Add a const_cast to make chromium build.

gfe-relnote: n/a (test only change)
PiperOrigin-RevId: 260889782
Change-Id: Ia59c1c217939cf196894041a207749c57ce06855

quic/core/http/quic_spdy_stream_test.cc

diff --git a/quic/core/http/quic_spdy_stream_test.cc b/quic/core/http/quic_spdy_stream_test.cc
index ab90036..37d04c2 100644
--- a/quic/core/http/quic_spdy_stream_test.cc
+++ b/quic/core/http/quic_spdy_stream_test.cc
@@ -235,7 +235,7 @@
                           payload.size();
     frame.resize(length);
 
-    QuicDataWriter writer(length, frame.data());
+    QuicDataWriter writer(length, const_cast<char*>(frame.data()));
     writer.WriteVarInt62(frame_type);
     writer.WriteStringPieceVarInt62(payload);
     // Even though integers can be encoded with different lengths,