[modules] Maintain array of cells for imports and local exports.

src/ast/modules.cc

Index: src/ast/modules.cc
diff --git a/src/ast/modules.cc b/src/ast/modules.cc
index 44bffa7bd2c6d4787652916618a1b5ac9e207128..5bd3b9bd34b3ee2647035cbd1acb48a392536ca6 100644
--- a/src/ast/modules.cc
+++ b/src/ast/modules.cc
@@ -212,6 +212,13 @@ void ModuleDescriptor::MakeIndirectExportsExplicit(Zone* zone) {
   }
 }
 
+ModuleDescriptor::CellIndexKind ModuleDescriptor::cell_index_kind(
+    int cell_index) {
+  if (cell_index > 0) return kExport;
+  if (cell_index < 0) return kImport;
+  return kInvalid;
+}
+
 void ModuleDescriptor::AssignCellIndices() {
   int export_index = 1;
   for (auto it = regular_exports_.begin(); it != regular_exports_.end();) {