src: update SFI script accessor for V8 8.1

The metadata used to access the script field from an SFI changed on V8
8.1. The field is still the same, so no other changes are necessary.
This fixes `v8 bt` on 8.1, as well as `stack-test` suite.

src/llv8-constants.cc

@@ -198,7 +198,8 @@ void SharedInfo::Load() {
                    "class_SharedFunctionInfo__function_identifier__Object");
   kScriptOffset = LoadConstant("class_SharedFunctionInfo__script__Object");
   kScriptOrDebugInfoOffset =
-      LoadConstant("class_SharedFunctionInfo__script_or_debug_info__Object");
+      LoadConstant({"class_SharedFunctionInfo__script_or_debug_info__Object",
+                    "class_SharedFunctionInfo__script_or_debug_info__HeapObject"});
   kStartPositionOffset =
       LoadConstant("class_SharedFunctionInfo__start_position_and_type__int",
                    "class_SharedFunctionInfo__start_position_and_type__SMI");

src/llv8-constants.h

@@ -157,7 +157,7 @@ class SharedInfo : public Module {
   int64_t kNameOffset;
   int64_t kInferredNameOffset;
   int64_t kScriptOffset;
-  int64_t kScriptOrDebugInfoOffset;
+  Constant<int64_t> kScriptOrDebugInfoOffset;
   int64_t kStartPositionOffset;
   int64_t kEndPositionOffset;
   int64_t kParameterCountOffset;

src/llv8-inl.h

@@ -444,7 +444,7 @@ ACCESSOR(SharedFunctionInfo, name, shared_info()->kNameOffset, String)
 ACCESSOR(SharedFunctionInfo, inferred_name, shared_info()->kInferredNameOffset,
          Value)
 ACCESSOR(SharedFunctionInfo, script, shared_info()->kScriptOffset, Script)
-ACCESSOR(SharedFunctionInfo, script_or_debug_info,
+SAFE_ACCESSOR(SharedFunctionInfo, script_or_debug_info,
          shared_info()->kScriptOrDebugInfoOffset, HeapObject)
 ACCESSOR(SharedFunctionInfo, scope_info, shared_info()->kScopeInfoOffset,
          HeapObject)
@@ -493,7 +493,9 @@ HeapObject SharedFunctionInfo::GetScopeInfo(Error& err) {
 }
 
 Script SharedFunctionInfo::GetScript(Error& err) {
-  if (v8()->shared_info()->kScriptOrDebugInfoOffset == -1) return script(err);
+  if (!v8()->shared_info()->kScriptOrDebugInfoOffset.Loaded()) {
+    return script(err);
+  }
 
   HeapObject maybe_script = script_or_debug_info(err);
   if (maybe_script.IsScript(err)) return maybe_script;