Add Dart_IsFuture. To be used in Dartium implementation of Promises.

runtime/vm/dart_api_impl.cc

Index: runtime/vm/dart_api_impl.cc
diff --git a/runtime/vm/dart_api_impl.cc b/runtime/vm/dart_api_impl.cc
index d354726ad32fc1ed15a940ca264be2b9e9582e1f..1f5fb044469c778d068b8e487b5aa22f2e99b720 100644
--- a/runtime/vm/dart_api_impl.cc
+++ b/runtime/vm/dart_api_impl.cc
@@ -71,9 +71,9 @@ static RawInstance* GetListInstance(Isolate* isolate, const Object& obj) {
     const Instance& instance = Instance::Cast(obj);
     const Class& obj_class = Class::Handle(isolate, obj.clazz());
     Error& malformed_type_error = Error::Handle(isolate);
-    if (obj_class.IsSubtypeOf(TypeArguments::Handle(isolate),
+    if (obj_class.IsSubtypeOf(Object::null_type_arguments(),
                               list_class,
-                              TypeArguments::Handle(isolate),
+                              Object::null_type_arguments(),
                               &malformed_type_error)) {
       ASSERT(malformed_type_error.IsNull());  // Type is a raw List.
       return instance.raw();
@@ -91,9 +91,9 @@ static RawInstance* GetMapInstance(Isolate* isolate, const Object& obj) {
     const Instance& instance = Instance::Cast(obj);
     const Class& obj_class = Class::Handle(isolate, obj.clazz());
     Error& malformed_type_error = Error::Handle(isolate);
-    if (obj_class.IsSubtypeOf(TypeArguments::Handle(isolate),
+    if (obj_class.IsSubtypeOf(Object::null_type_arguments(),
                               map_class,
-                              TypeArguments::Handle(isolate),
+                              Object::null_type_arguments(),
                               &malformed_type_error)) {
       ASSERT(malformed_type_error.IsNull());  // Type is a raw Map.
       return instance.raw();
@@ -1870,6 +1870,30 @@ DART_EXPORT bool Dart_IsByteBuffer(Dart_Handle handle) {
 }
 
 
+DART_EXPORT bool Dart_IsFuture(Dart_Handle handle) {
+  TRACE_API_CALL(CURRENT_FUNC);
+  Isolate* isolate = Isolate::Current();
+  DARTSCOPE(isolate);
+  const Object& obj = Object::Handle(isolate, Api::UnwrapHandle(handle));
+  if (obj.IsInstance()) {
+    const Library& async_lib =
+        Library::Handle(isolate, Library::AsyncLibrary());
+    const Class& future_class =
+        Class::Handle(isolate, async_lib.LookupClass(Symbols::Future()));
+    ASSERT(!future_class.IsNull());
+    const Class& obj_class = Class::Handle(isolate, obj.clazz());
+    Error& malformed_type_error = Error::Handle(isolate);
+    bool is_future = obj_class.IsSubtypeOf(Object::null_type_arguments(),
+                                           future_class,
+                                           Object::null_type_arguments(),
+                                           &malformed_type_error);
+    ASSERT(malformed_type_error.IsNull());  // Type is a raw Future.
+    return is_future;
+  }
+  return false;
+}
+
+
 // --- Instances ----
 
 DART_EXPORT Dart_Handle Dart_InstanceGetType(Dart_Handle instance) {