Make down-conversion explicit from CFX_ByteString to CFX_ByteStringC.

core/fxcrt/fx_basic_buffer.cpp

Index: core/fxcrt/fx_basic_buffer.cpp
diff --git a/core/fxcrt/fx_basic_buffer.cpp b/core/fxcrt/fx_basic_buffer.cpp
index 28c8ac0f3271bce3ddfb210e12b7dc35375feeaa..de7bff24018284e717af3ccf769f2859f5e431b4 100644
--- a/core/fxcrt/fx_basic_buffer.cpp
+++ b/core/fxcrt/fx_basic_buffer.cpp
@@ -248,7 +248,7 @@ CFX_ArchiveSaver& CFX_ArchiveSaver::operator<<(const FX_WCHAR* wstr) {
 }
 CFX_ArchiveSaver& CFX_ArchiveSaver::operator<<(const CFX_WideString& wstr) {
   CFX_ByteString encoded = wstr.UTF16LE_Encode();
-  return operator<<(encoded);
+  return operator<<(encoded.AsByteStringC());
 }
 void CFX_ArchiveSaver::Write(const void* pData, FX_STRSIZE dwSize) {
   if (m_pStream) {