Move WidgetActivationWaiter to a common place

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"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/views/test/views_test_base.h"
 #include "ui/views/widget/widget_delegate.h"
+#include "ui/views/widget/widget_observer.h"
 
 namespace ui {
 namespace internal {
 class InputMethodDelegate;
 }
 class EventProcessor;
 }
 
 namespace views {
 
@@ skipping 123 matching lines @@
 
   // WidgetDelegate override:
   View* GetInitiallyFocusedView() override;
 
  private:
   View* view_;
 
   DISALLOW_COPY_AND_ASSIGN(TestInitialFocusWidgetDelegate);
 };
 
+// Spins a run loop until a Widget's activation reaches the desired state.
+class WidgetActivationWaiter : public WidgetObserver {
+ public:
+  WidgetActivationWaiter(Widget* widget, bool active);
+  ~WidgetActivationWaiter() override;
+
+  void Wait();

[sky, 2016/10/12 16:05:43]

Document what this does.

[Qiang(Joe) Xu, 2016/10/12 16:55:58]

Done.

+
+ private:
+  // views::WidgetObserver override:
+  void OnWidgetActivationChanged(Widget* widget, bool active) override;
+
+  base::RunLoop run_loop_;
+  bool observed_;
+  bool active_;
+
+  DISALLOW_COPY_AND_ASSIGN(WidgetActivationWaiter);
+};
+
 }  // namespace test
 }  // namespace views
 
 #endif  // UI_VIEWS_TEST_WIDGET_TEST_H_