Only Update the Scale Factor if the Scale Factor Actually Changed

ui/display/win/screen_win.h

 // Copyright (c) 2012 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_DISPLAY_WIN_SCREEN_WIN_H_
 #define UI_DISPLAY_WIN_SCREEN_WIN_H_
 
 #include <windows.h>
 
 #include <memory>
@@ skipping 74 matching lines @@
   // The DPI scale is performed relative to the display nearest to |hwnd|.
   static gfx::Size ScreenToDIPSize(HWND hwnd, const gfx::Size& size_in_pixels);
 
   // Converts a DIP size to a physical size.
   // The DPI scale is performed relative to the display nearest to |hwnd|.
   static gfx::Size DIPToScreenSize(HWND hwnd, const gfx::Size& dip_size);
 
   // Returns the result of GetSystemMetrics for |metric| scaled to |hwnd|'s DPI.
   static int GetSystemMetricsForHwnd(HWND hwnd, int metric);
 
+  // Returns |hwnd|'s scale factor.
+  static float GetScaleFactorForHWND(HWND hwnd);
+
   // Returns the HWND associated with the NativeView.
   virtual HWND GetHWNDFromNativeView(gfx::NativeView window) const;
 
   // Returns the NativeView associated with the HWND.
   virtual gfx::NativeWindow GetNativeWindowFromHWND(HWND hwnd) const;
 
  protected:
   // display::Screen:
   gfx::Point GetCursorScreenPoint() override;
   bool IsWindowUnderCursor(gfx::NativeWindow window) override;
@@ skipping 47 matching lines @@
 
   // Returns the ScreenWinDisplay closest to or enclosing |dip_rect|.
   ScreenWinDisplay GetScreenWinDisplayNearestDIPRect(
       const gfx::Rect& dip_rect) const;
 
   // Returns the ScreenWinDisplay corresponding to the primary monitor.
   ScreenWinDisplay GetPrimaryScreenWinDisplay() const;
 
   ScreenWinDisplay GetScreenWinDisplay(const MONITORINFOEX& monitor_info) const;
 
-  static float GetScaleFactorForHWND(HWND hwnd);
-
   // Returns the result of calling |getter| with |value| on the global
   // ScreenWin if it exists, otherwise return the default ScreenWinDisplay.
   template <typename Getter, typename GetterType>
   static ScreenWinDisplay GetScreenWinDisplayVia(Getter getter,
                                                  GetterType value);
 
   void RecordDisplayScaleFactors() const;
 
   // Helper implementing the DisplayObserver handling.
   DisplayChangeNotifier change_notifier_;
 
   std::unique_ptr<gfx::SingletonHwndObserver> singleton_hwnd_observer_;
 
   // Current list of ScreenWinDisplays.
   std::vector<ScreenWinDisplay> screen_win_displays_;
 
   DISALLOW_COPY_AND_ASSIGN(ScreenWin);
 };
 
 }  // namespace win
 }  // namespace display
 
 #endif  // UI_DISPLAY_WIN_SCREEN_WIN_H_