Internalize strings in-place

src/heap/objects-visiting.cc

Index: src/heap/objects-visiting.cc
diff --git a/src/heap/objects-visiting.cc b/src/heap/objects-visiting.cc
index 9458739b1f6d3f55d9d28509ba4f953241bf7fa0..2ae784ea86c441641612522d03753c83df0f78ee 100644
--- a/src/heap/objects-visiting.cc
+++ b/src/heap/objects-visiting.cc
@@ -41,6 +41,9 @@ StaticVisitorBase::VisitorId StaticVisitorBase::GetVisitorId(
       case kExternalStringTag:
         return GetVisitorIdForSize(kVisitDataObject, kVisitDataObjectGeneric,
                                    instance_size, has_unboxed_fields);
+
+      case kThinStringTag:
+        return kVisitThinString;
     }
     UNREACHABLE();
   }