Reland of [wasm] Add tests for JS wrappers to test-run-wasm.

src/wasm/wasm-js.cc

Index: src/wasm/wasm-js.cc
diff --git a/src/wasm/wasm-js.cc b/src/wasm/wasm-js.cc
index d8b2822c9b0c2e2bdaac4724d9be4987667f30b2..80d8bdb2369e1b87e4fbf3427c19660f4a3e3bb6 100644
--- a/src/wasm/wasm-js.cc
+++ b/src/wasm/wasm-js.cc
@@ -307,18 +307,15 @@ static void InstallFunc(Isolate* isolate, Handle<JSObject> object,
 
 void WasmJs::Install(Isolate* isolate, Handle<JSGlobalObject> global) {
   // Setup wasm function map.
-  Handle<Map> wasm_function_map = isolate->factory()->NewMap(
-      JS_FUNCTION_TYPE, JSFunction::kSize + kPointerSize);
-  wasm_function_map->set_is_callable();
-  global->native_context()->set_wasm_function_map(*wasm_function_map);
+  Handle<Context> context(global->native_context(), isolate);
+  InstallWasmFunctionMap(isolate, context);
 
   // Bind the WASM object.
   Factory* factory = isolate->factory();
   Handle<String> name = v8_str(isolate, "_WASMEXP_");
   Handle<JSFunction> cons = factory->NewFunction(name);
   JSFunction::SetInstancePrototype(
-      cons, Handle<Object>(global->native_context()->initial_object_prototype(),
-                           isolate));
+      cons, Handle<Object>(context->initial_object_prototype(), isolate));
   cons->shared()->set_instance_class_name(*name);
   Handle<JSObject> wasm_object = factory->NewJSObject(cons, TENURED);
   PropertyAttributes attributes = static_cast<PropertyAttributes>(DONT_ENUM);
@@ -333,5 +330,16 @@ void WasmJs::Install(Isolate* isolate, Handle<JSGlobalObject> global) {
   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);
+  }
+}
+
 }  // namespace internal
 }  // namespace v8