[ios] Removes an unneeded UIWindow from HardwareKeyboardWatcherTest.

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

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/chrome/browser/ui/keyboard/hardware_keyboard_watcher.h"
 
 #include "base/mac/scoped_nsobject.h"
 #include "base/test/histogram_tester.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/platform_test.h"
 #import "third_party/ocmock/OCMock/OCMock.h"
 
 namespace {
 
 void PostKeyboardWillChangeNotification(CGRect beginFrame, CGRect endFrame) {
   [[NSNotificationCenter defaultCenter]
       postNotificationName:UIKeyboardWillChangeFrameNotification
                     object:nil
                   userInfo:@{
                     UIKeyboardFrameBeginUserInfoKey :
                         [NSValue valueWithCGRect:beginFrame],
                     UIKeyboardFrameEndUserInfoKey :
                         [NSValue valueWithCGRect: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;
   id mockView = [OCMockObject niceMockForClass:[UIView class]];
   [[mockView stub] andReturn:nil];
   base::scoped_nsobject<HardwareKeyboardWatcher> watcher(
       [[HardwareKeyboardWatcher alloc] initWithAccessoryView:mockView]);
 
   PostKeyboardWillChangeNotification(CGRectZero, CGRectZero);
   PostKeyboardWillChangeNotification(CGRectInfinite, CGRectInfinite);
@@ skipping 71 matching lines @@
       [[HardwareKeyboardWatcher alloc] initWithAccessoryView:mockView]);
 
   PostKeyboardWillChangeNotification(CGRectMake(0, -50, 100, 100),
                                      CGRectMake(0, 0, 100, 100));
 
   histogram_tester.ExpectUniqueSample("Omnibox.HardwareKeyboardModeEnabled",
                                       true, 1);
 }
 
 }  // namespace