Use instance type in Object.prototype.toString().

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index aeded64a892aee49504144471c4f6ede80dafd22..fdd83e75da830603e45a358f6e51f15782d1d049 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -2068,6 +2068,10 @@ int JSObject::GetHeaderSize(InstanceType type) {
       return JSObject::kHeaderSize;
     case JS_MESSAGE_OBJECT_TYPE:
       return JSMessageObject::kSize;
+    case JS_ARGUMENTS_TYPE:
+      return JSArgumentsObject::kHeaderSize;
+    case JS_ERROR_TYPE:
+      return JSObject::kHeaderSize;
     default:
       UNREACHABLE();
       return 0;