Implement rudimentary module linking.

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index 3392927f014e16be990f24be269852274b71593e..d2cc08848fa669948c276715cb116b1ffee6c315 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -581,7 +581,8 @@ bool Object::IsContext() {
             map == heap->catch_context_map() ||
             map == heap->with_context_map() ||
             map == heap->global_context_map() ||
-            map == heap->block_context_map());
+            map == heap->block_context_map() ||
+            map == heap->module_context_map());
   }
   return false;
 }
@@ -594,6 +595,13 @@ bool Object::IsGlobalContext() {
 }
 
 
+bool Object::IsModuleContext() {
+  return Object::IsHeapObject() &&
+      HeapObject::cast(this)->map() ==
+      HeapObject::cast(this)->GetHeap()->module_context_map();
+}
+
+
 bool Object::IsScopeInfo() {
   return Object::IsHeapObject() &&
       HeapObject::cast(this)->map() ==
@@ -613,6 +621,7 @@ TYPE_CHECKER(Code, CODE_TYPE)
 TYPE_CHECKER(Oddball, ODDBALL_TYPE)
 TYPE_CHECKER(JSGlobalPropertyCell, JS_GLOBAL_PROPERTY_CELL_TYPE)
 TYPE_CHECKER(SharedFunctionInfo, SHARED_FUNCTION_INFO_TYPE)
+TYPE_CHECKER(JSModule, JS_MODULE_TYPE)
 TYPE_CHECKER(JSValue, JS_VALUE_TYPE)
 TYPE_CHECKER(JSDate, JS_DATE_TYPE)
 TYPE_CHECKER(JSMessageObject, JS_MESSAGE_OBJECT_TYPE)
@@ -1430,6 +1439,8 @@ int JSObject::GetHeaderSize() {
   // field operations considerably on average.
   if (type == JS_OBJECT_TYPE) return JSObject::kHeaderSize;
   switch (type) {
+    case JS_MODULE_TYPE:
+      return JSModule::kSize;
     case JS_GLOBAL_PROXY_TYPE:
       return JSGlobalProxy::kSize;
     case JS_GLOBAL_OBJECT_TYPE:
@@ -4126,6 +4137,16 @@ void Foreign::set_foreign_address(Address value) {
 }
 
 
+ACCESSORS(JSModule, context, Object, kContextOffset)
+
+
+JSModule* JSModule::cast(Object* obj) {
+  ASSERT(obj->IsJSModule());
+  ASSERT(HeapObject::cast(obj)->Size() == JSModule::kSize);
+  return reinterpret_cast<JSModule*>(obj);
+}
+
+
 ACCESSORS(JSValue, value, Object, kValueOffset)