Emit OnNativeWidgetDestroying() before clearing the NSWindowDelegate.

ui/views/widget/widget_unittest.cc

 // Copyright (c) 2012 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 <algorithm>
 #include <memory>
 #include <set>
 
 #include "base/bind.h"
 #include "base/macros.h"
@@ skipping 2060 matching lines @@
 class WidgetBoundsObserver : public WidgetObserver {
  public:
   WidgetBoundsObserver() {}
   ~WidgetBoundsObserver() override {}
 
   gfx::Rect bounds() { return bounds_; }
 
   // WidgetObserver:
   void OnWidgetDestroying(Widget* widget) override {
     EXPECT_TRUE(widget->GetNativeWindow());
+    EXPECT_TRUE(Widget::GetWidgetForNativeWindow(widget->GetNativeWindow()));
     bounds_ = widget->GetWindowBoundsInScreen();
   }
 
  private:
   gfx::Rect bounds_;
 
   DISALLOW_COPY_AND_ASSIGN(WidgetBoundsObserver);
 };
 
 // Verifies Close() results in destroying.
@@ skipping 1737 matching lines @@
     Transparency_DesktopWidgetTranslucent
 #endif
 TEST_F(CompositingWidgetTest, MAYBE_Transparency_DesktopWidgetTranslucent) {
   CheckAllWidgetsForOpacity(Widget::InitParams::TRANSLUCENT_WINDOW);
 }
 
 #endif  // !defined(OS_CHROMEOS)
 
 }  // namespace test
 }  // namespace views