record that Gamepad.buttons creates GamepadButtons

tests/html/gamepad_test.dart

-library ClientRectTest;
 import 'package:unittest/unittest.dart';
 import 'package:unittest/html_config.dart';
 import 'dart:html';
 
 main() {
-
-  var isRectList =
-      predicate((x) => x is List<Rectangle>, 'is a List<Rectangle>');
+  var isGamepadList =
+      predicate((x) => x is List<Gamepad>, 'is a List<Gamepad>');
 
   insertTestDiv() {
     var element = new Element.tag('div');
     element.innerHtml = r'''
     A large block of text should go here. Click this
     block of text multiple times to see each line
     highlight with every click of the mouse button.
     ''';
     document.body.append(element);
     return element;
   }
 
   useHtmlConfiguration();
 
-   test("ClientRectList test", () {
+  test("getGamepads", () {
     insertTestDiv();
-    var range = new Range();
-    var rects = range.getClientRects();
-    expect(rects, isRectList);
+    var gamepads = window.navigator.getGamepads();
+    expect(gamepads, isGamepadList);
+    for (var gamepad in gamepads) {
+      if (gamepad != null) {
+        expect(gamepad.id, isNotNull);
+      }
+    }
   });
 }