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

runtime/vm/dart_api_impl_test.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "bin/builtin.h"
 #include "include/dart_api.h"
 #include "include/dart_debugger_api.h"
 #include "include/dart_mirrors_api.h"
 #include "include/dart_native_api.h"
 #include "platform/assert.h"
@@ skipping 1366 matching lines @@
   result = Dart_ListGetAt(keys, 1);
   EXPECT(Dart_IsString(result));
   equals = false;
   EXPECT_VALID(Dart_ObjectEquals(result, b, &equals));
   EXPECT(equals);
 
   EXPECT(Dart_IsError(Dart_MapKeys(a)));
 }
 
 
+TEST_CASE(IsFuture) {
+  const char* kScriptChars =
+      "import 'dart:async';"
+      "Future testMain() {"
+      "  return new Completer().future;"
+      "}";
+  Dart_Handle result;
+
+  // Create a test library and Load up a test script in it.
+  Dart_Handle lib = TestCase::LoadTestScript(kScriptChars, NULL);
+
+  // Invoke a function which returns an object of type Future.
+  result = Dart_Invoke(lib, NewString("testMain"), 0, NULL);
+  EXPECT_VALID(result);
+  EXPECT(Dart_IsFuture(result));
+
+  EXPECT(!Dart_IsFuture(lib));  // Non-instance.
+  Dart_Handle anInteger = Dart_NewInteger(0);
+  EXPECT(!Dart_IsFuture(anInteger));
+  Dart_Handle aString = NewString("I am not a Future");
+  EXPECT(!Dart_IsFuture(aString));
+  Dart_Handle null = Dart_Null();
+  EXPECT(!Dart_IsFuture(null));
+}
+
+
 TEST_CASE(TypedDataViewListGetAsBytes) {
   const int kSize = 1000;
 
   const char* kScriptChars =
       "import 'dart:typed_data';\n"
       "List main(int size) {\n"
       "  var a = new Int8List(size);\n"
       "  var view = new Int8List.view(a.buffer, 0, size);\n"
       "  return view;\n"
       "}\n";
@@ skipping 7269 matching lines @@
                                    NewString("main"),
                                    1,
                                    dart_args);
   int64_t value = 0;
   result = Dart_IntegerToInt64(result, &value);
   EXPECT_VALID(result);
   EXPECT_EQ(6, value);
 }
 
 }  // namespace dart