[ios] Removes an unneeded UIWindow from HardwareKeyboardWatcherTest.

ios/chrome/browser/ui/keyboard/hardware_keyboard_watcher_unittest.mm

Index: ios/chrome/browser/ui/keyboard/hardware_keyboard_watcher_unittest.mm
diff --git a/ios/chrome/browser/ui/keyboard/hardware_keyboard_watcher_unittest.mm b/ios/chrome/browser/ui/keyboard/hardware_keyboard_watcher_unittest.mm
index a820788d41ed8439f17c9f35c75787e2ea5cc21c..6200e151ad0339a7d6df51274d7a2b995e91cad0 100644
--- a/ios/chrome/browser/ui/keyboard/hardware_keyboard_watcher_unittest.mm
+++ b/ios/chrome/browser/ui/keyboard/hardware_keyboard_watcher_unittest.mm
@@ -24,17 +24,7 @@ void PostKeyboardWillChangeNotification(CGRect beginFrame, CGRect endFrame) {
                   }];
 }
 
-class HardwareKeyboardWatcherTest : public PlatformTest {
- public:
-  HardwareKeyboardWatcherTest() {
-    _window.reset(
-        [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]]);
-    [_window makeKeyAndVisible];
-  }
-
- protected:
-  base::scoped_nsobject<UIWindow> _window;
-};
+typedef PlatformTest HardwareKeyboardWatcherTest;
 
 TEST_F(HardwareKeyboardWatcherTest, AccessoryViewNotInHierarchy_NoHistogram) {
   base::HistogramTester histogram_tester;