[wasm] Get rid of extra wrappers when import another wasm export

src/wasm/wasm-js.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/api-natives.h"
 #include "src/api.h"
 #include "src/asmjs/asm-typer.h"
 #include "src/asmjs/asm-wasm-builder.h"
 #include "src/assert-scope.h"
 #include "src/ast/ast.h"
@@ skipping 528 matching lines @@
   if (!context->get(Context::WASM_FUNCTION_MAP_INDEX)->IsMap()) {
     // TODO(titzer): Move this to bootstrapper.cc??
     // TODO(titzer): Also make one for strict mode functions?
     Handle<Map> prev_map = Handle<Map>(context->sloppy_function_map(), isolate);
 
     InstanceType instance_type = prev_map->instance_type();
     int internal_fields = JSObject::GetInternalFieldCount(*prev_map);
     CHECK_EQ(0, internal_fields);
     int pre_allocated =
         prev_map->GetInObjectProperties() - prev_map->unused_property_fields();
-    int instance_size;
-    int in_object_properties;
-    JSFunction::CalculateInstanceSizeHelper(instance_type, internal_fields + 1,
+    int instance_size = 0;
+    int in_object_properties = 0;
+    int wasm_internal_fields = internal_fields + 1  // module instance object
+                               + 1                  // function arity
+                               + 1;                 // function signature
+    JSFunction::CalculateInstanceSizeHelper(instance_type, wasm_internal_fields,
                                             0, &instance_size,
                                             &in_object_properties);
 
     int unused_property_fields = in_object_properties - pre_allocated;
     Handle<Map> map = Map::CopyInitialMap(
         prev_map, instance_size, in_object_properties, unused_property_fields);
 
     context->set_wasm_function_map(*map);
   }
 }
 
 }  // namespace internal
 }  // namespace v8