[wasm] Create a proper map for functions created from WASM.

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.h"
 #include "src/api-natives.h"
 #include "src/assert-scope.h"
 #include "src/ast/ast.h"
 #include "src/ast/scopes.h"
 #include "src/factory.h"
@@ skipping 289 matching lines @@
   InstallFunc(isolate, wasm_object, "verifyModule", VerifyModule);
   InstallFunc(isolate, wasm_object, "verifyFunction", VerifyFunction);
   InstallFunc(isolate, wasm_object, "instantiateModule", InstantiateModule);
   InstallFunc(isolate, wasm_object, "instantiateModuleFromAsm",
               InstantiateModuleFromAsm);
 }
 
 
 void WasmJs::InstallWasmFunctionMap(Isolate* isolate, Handle<Context> context) {
   if (!context->get(Context::WASM_FUNCTION_MAP_INDEX)->IsMap()) {
-    Handle<Map> wasm_function_map = isolate->factory()->NewMap(
-        JS_FUNCTION_TYPE, JSFunction::kSize + kPointerSize);
-    wasm_function_map->set_is_callable();
-    context->set_wasm_function_map(*wasm_function_map);
+    // 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,
+                                            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