Support device scale factor test with popups in LayoutTest

ui/views/widget/desktop_aura/desktop_screen_x11.h

 // Copyright (c) 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_WIDGET_DESKTOP_AURA_DESKTOP_SCREEN_X11_H_
 #define UI_VIEWS_WIDGET_DESKTOP_AURA_DESKTOP_SCREEN_X11_H_
 
 #include "base/timer/timer.h"
 #include "ui/events/platform/platform_event_dispatcher.h"
 #include "ui/gfx/display_change_notifier.h"
@@ skipping 29 matching lines @@
   gfx::Display GetDisplayNearestPoint(const gfx::Point& point) const override;
   gfx::Display GetDisplayMatching(const gfx::Rect& match_rect) const override;
   gfx::Display GetPrimaryDisplay() const override;
   void AddObserver(gfx::DisplayObserver* observer) override;
   void RemoveObserver(gfx::DisplayObserver* observer) override;
 
   // ui::PlatformEventDispatcher:
   bool CanDispatchEvent(const ui::PlatformEvent& event) override;
   uint32_t DispatchEvent(const ui::PlatformEvent& event) override;
 
+  static void UpdateDeviceScaleFactorForTest();
+
  private:
   friend class DesktopScreenX11Test;
 
   // Constructor used in tests.
   DesktopScreenX11(const std::vector<gfx::Display>& test_displays);
 
   // Builds a list of displays from the current screen information offered by
   // the X server.
   std::vector<gfx::Display> BuildDisplaysFromXRandRInfo();
 
@@ skipping 18 matching lines @@
   scoped_ptr<base::OneShotTimer> configure_timer_;
 
   gfx::DisplayChangeNotifier change_notifier_;
 
   DISALLOW_COPY_AND_ASSIGN(DesktopScreenX11);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_WIDGET_DESKTOP_AURA_DESKTOP_SCREEN_X11_H_