[modules] Implement namespace imports.

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index af1261538e2b553e6bdac16a9a6357da5d1411bb..bfe0965b24fd4e980fd286e8b5dee35ce77cd928 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -3279,6 +3279,7 @@ CAST_ACCESSOR(JSGlobalProxy)
 CAST_ACCESSOR(JSMap)
 CAST_ACCESSOR(JSMapIterator)
 CAST_ACCESSOR(JSMessageObject)
+CAST_ACCESSOR(JSModuleNamespace)
 CAST_ACCESSOR(JSObject)
 CAST_ACCESSOR(JSProxy)
 CAST_ACCESSOR(JSReceiver)
@@ -5712,8 +5713,11 @@ BOOL_ACCESSORS(PrototypeInfo, bit_field, should_be_fast_map, kShouldBeFastBit)
 ACCESSORS(ContextExtension, scope_info, ScopeInfo, kScopeInfoOffset)
 ACCESSORS(ContextExtension, extension, Object, kExtensionOffset)
 
+ACCESSORS(JSModuleNamespace, module, Module, kModuleOffset)
+
 ACCESSORS(Module, code, Object, kCodeOffset)
 ACCESSORS(Module, exports, ObjectHashTable, kExportsOffset)
+ACCESSORS(Module, module_namespace, HeapObject, kModuleNamespaceOffset)
 ACCESSORS(Module, requested_modules, FixedArray, kRequestedModulesOffset)
 SMI_ACCESSORS(Module, flags, kFlagsOffset)
 BOOL_ACCESSORS(Module, flags, evaluated, kEvaluatedBit)
@@ -6674,6 +6678,8 @@ bool JSGeneratorObject::is_executing() const {
   return continuation() == kGeneratorExecuting;
 }
 
+TYPE_CHECKER(JSModuleNamespace, JS_MODULE_NAMESPACE_TYPE)
+
 ACCESSORS(JSValue, value, Object, kValueOffset)