Serializer: simplify external reference encoding.

src/disassembler.cc

Index: src/disassembler.cc
diff --git a/src/disassembler.cc b/src/disassembler.cc
index 37e0c83f80f7561de32658e22eb25dbd7823ae94..9eff9266532cd68fcdf14e033cca58363080caba 100644
--- a/src/disassembler.cc
+++ b/src/disassembler.cc
@@ -185,8 +185,8 @@ static int DecodeIt(Isolate* isolate, std::ostream* os,
         SmartArrayPointer<const char> obj_name = accumulator.ToCString();
         out.AddFormatted("    ;; object: %s", obj_name.get());
       } else if (rmode == RelocInfo::EXTERNAL_REFERENCE) {
-        const char* reference_name =
-            ref_encoder.NameOfAddress(relocinfo.target_external_reference());
+        const char* reference_name = ref_encoder.NameOfAddress(
+            isolate, relocinfo.target_external_reference());
         out.AddFormatted("    ;; external reference (%s)", reference_name);
       } else if (RelocInfo::IsCodeTarget(rmode)) {
         out.AddFormatted("    ;; code:");