Export the current data format version used by ValueSerializer.

src/value-serializer.cc

Index: src/value-serializer.cc
diff --git a/src/value-serializer.cc b/src/value-serializer.cc
index acedb4be329fcdf570785051993adbe95b7bef46..b26eed933cb955a2e98e0edaaba17b968ac09d49 100644
--- a/src/value-serializer.cc
+++ b/src/value-serializer.cc
@@ -154,6 +154,11 @@ enum class WasmEncodingTag : uint8_t {
 
 }  // namespace
 
+// static
+uint32_t ValueSerializer::GetCurrentDataFormatVersion() {
+  return kLatestVersion;
+}
+
 ValueSerializer::ValueSerializer(Isolate* isolate,
                                  v8::ValueSerializer::Delegate* delegate)
     : isolate_(isolate),