Fix mDNS registration using wrong hostname.

PiperOrigin-RevId: 803100146

internal/platform/implementation/windows/utils.h

@@ -19,6 +19,7 @@
 
 #include <cstddef>
 #include <cstdint>
+#include <optional>
 #include <string>
 #include <vector>
 
@@ -59,6 +60,9 @@ winrt::guid nearby_uuid_to_winrt_guid(Uuid uuid);
 bool is_nearby_uuid_equal_to_winrt_guid(const Uuid& uuid,
                                         const ::winrt::guid& guid);
 
+// Returns the DNS host name of the computer or std::nullopt if it fails.
+std::optional<std::wstring> GetDnsHostName();
+
 namespace Constants {
 // The Id of the Service Name SDP attribute
 const uint16_t SdpServiceNameAttributeId = 0x100;