Changes views_aura_mus_unittests to create DesktopNativeWidgetAura

ui/views/test/platform_test_helper_cocoa.mm

Index: ui/views/test/platform_test_helper_cocoa.mm
diff --git a/ui/views/test/platform_test_helper_cocoa.mm b/ui/views/test/platform_test_helper_cocoa.mm
new file mode 100644
index 0000000000000000000000000000000000000000..a934f58378ee38ada7f9f73d2e459b704a9a1b91
--- /dev/null
+++ b/ui/views/test/platform_test_helper_cocoa.mm
@@ -0,0 +1,27 @@
+// Copyright 2016 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.
+
+#include "ui/views/test/platform_test_helper.h"
+
+#include <Cocoa/Cocoa.h>
+
+#import "base/mac/scoped_nsobject.h"
+#import "base/mac/scoped_objc_class_swizzler.h"
+#include "base/macros.h"
+#include "base/memory/ptr_util.h"
+#import "ui/views/cocoa/bridged_native_widget.h"
+#include "ui/views/widget/native_widget_mac.h"
+#include "ui/views/widget/widget.h"
+
+namespace views {
+
+void PlatformTestHelper::SimulateNativeDestroy(Widget* widget) {
+  // Retain the window while closing it, otherwise the window may lose its
+  // last owner before -[NSWindow close] completes (this offends AppKit).
+  // Usually this reference will exist on an event delivered to the runloop.
+  base::scoped_nsobject<NSWindow> window([widget->GetNativeWindow() retain]);
+  [window close];
+}
+
+}  // namespace views