cleanup: make WidgetClosingObserver as test support

ui/views/test/widget_test.h

 // Copyright 2013 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.
 
 #ifndef UI_VIEWS_TEST_WIDGET_TEST_H_
 #define UI_VIEWS_TEST_WIDGET_TEST_H_
 
 #include "base/macros.h"
 #include "base/run_loop.h"
 #include "build/build_config.h"
@@ skipping 159 matching lines @@
   // views::WidgetObserver override:
   void OnWidgetActivationChanged(Widget* widget, bool active) override;
 
   base::RunLoop run_loop_;
   bool observed_;
   bool active_;
 
   DISALLOW_COPY_AND_ASSIGN(WidgetActivationWaiter);
 };
 
+// Use in tests to provide functionality to observe the widget passed in the
+// constructor for the widget closing event.
+class WidgetClosingObserver : public WidgetObserver {
+ public:
+  explicit WidgetClosingObserver(Widget* widget);
+  ~WidgetClosingObserver() override;
+
+  bool widget_closed() const { return !widget_; }
+
+ private:
+  // views::WidgetObserver override:
+  void OnWidgetClosing(Widget* widget) override;
+
+  Widget* widget_;
+
+  DISALLOW_COPY_AND_ASSIGN(WidgetClosingObserver);
+};
+
 }  // namespace test
 }  // namespace views
 
 #endif  // UI_VIEWS_TEST_WIDGET_TEST_H_