Emit OnNativeWidgetDestroying() before clearing the NSWindowDelegate.

ui/views/cocoa/bridged_native_widget.h

Index: ui/views/cocoa/bridged_native_widget.h
diff --git a/ui/views/cocoa/bridged_native_widget.h b/ui/views/cocoa/bridged_native_widget.h
index d1e2d08a516abbee267e4934cf6a2e15aee7b874..373580d956356b1cda8fc783fb011c3d722d08a7 100644
--- a/ui/views/cocoa/bridged_native_widget.h
+++ b/ui/views/cocoa/bridged_native_widget.h
@@ -321,6 +321,14 @@ class VIEWS_EXPORT BridgedNativeWidget
 
   AssociatedViews associated_views_;
 
+  // We will set this flag to false inside OnWindowWillClose().
+  // For teardown flows (e.g. Widget::WIDGET_OWNS_NATIVE_WIDGET or
+  // Widget::CloseNow()) we needs to be invoked manually OnWindowWillClose()
+  // in destructor.
+  // But [NSWindow close] would synchronously call OnWindowWillClose() so to
+  // prevent second call in destructor we use this flag.
+  bool close_window_ = true;
+
   DISALLOW_COPY_AND_ASSIGN(BridgedNativeWidget);
 };