Emit OnNativeWidgetDestroying() before clearing the NSWindowDelegate.

chrome/browser/ui/views/frame/browser_view_browsertest_mac.mm

+// 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.
+
+#import <Cocoa/Cocoa.h>
+
+#include "base/macros.h"
+#include "chrome/browser/ui/browser.h"
+#include "chrome/browser/ui/browser_tabstrip.h"
+#include "chrome/browser/ui/tabs/tab_strip_model.h"
+#include "chrome/browser/ui/views/frame/browser_view.h"
+#include "chrome/test/base/in_process_browser_test.h"
+
+using BrowserViewTestMac = InProcessBrowserTest;
+
+IN_PROC_BROWSER_TEST_F(BrowserViewTestMac, CloseWithTabsStartWithActive) {
+  chrome::AddTabAt(browser(), GURL(), -1, true);
+  chrome::AddTabAt(browser(), GURL(), -1, true);
+  browser()->tab_strip_model()->ActivateTabAt(0, true);
+  NSWindow* window = BrowserView::GetBrowserViewForBrowser(browser())
+      ->GetWidget()->GetNativeWindow();
+  [window close];
+}

[tapted, 2016/10/05 08:38:18]

this isn't the right place for a test, and there are no expectations here, and
no comments.

The tests belong in widget_unittest.cc -- we need to ensure platforms are
consistent.

There is already a test there:
// Test that the NativeWidget is still valid during OnNativeWidgetDestroying(),
// and properties that depend on it are valid, when closed via Close().
TEST_F(WidgetTest, ValidDuringOnNativeWidgetDestroyingFromClose) 


If you change WidgetBoundsObserver::OnWidgetDestroying() to something like

  // WidgetObserver:
  void OnWidgetDestroying(Widget* widget) override {
    EXPECT_TRUE(widget->GetNativeWindow());
    EXPECT_TRUE(Widget::GetWidgetForNativeWindow(widget->GetNativeWindow()));
    bounds_ = widget->GetWindowBoundsInScreen();
  }

I think this will give proper coverage for what we're interested in here.