Only Update the Scale Factor if the Scale Factor Actually Changed

ui/display/win/screen_win.cc

 // 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.
 
 #include "ui/display/win/screen_win.h"
 
 #include <windows.h>
 #include <shellscalingapi.h>
 
 #include <algorithm>
@@ skipping 295 matching lines @@
   Display primary_display(g_screen_win_instance->GetPrimaryDisplay());
   int system_metrics_result = g_screen_win_instance->GetSystemMetrics(metric);
 
   float metrics_relative_scale_factor = hwnd
       ? GetScaleFactorForHWND(hwnd) / primary_display.device_scale_factor()
       : 1.0f;
   return static_cast<int>(std::round(
       system_metrics_result * metrics_relative_scale_factor));
 }
 
+// static
+float ScreenWin::GetScaleFactorForHWND(HWND hwnd) {
+  if (!g_screen_win_instance)
+    return ScreenWinDisplay().display().device_scale_factor();
+
+  DCHECK(hwnd);
+  HWND rootHwnd = g_screen_win_instance->GetRootWindow(hwnd);
+  ScreenWinDisplay screen_win_display =
+      g_screen_win_instance->GetScreenWinDisplayNearestHWND(rootHwnd);
+  return screen_win_display.display().device_scale_factor();
+}
+
 HWND ScreenWin::GetHWNDFromNativeView(gfx::NativeView window) const {
   NOTREACHED();
   return nullptr;
 }
 
 gfx::NativeWindow ScreenWin::GetNativeWindowFromHWND(HWND hwnd) const {
   NOTREACHED();
   return nullptr;
 }
 
@@ skipping 196 matching lines @@
       return screen_win_display;
   }
   // There is 1:1 correspondence between MONITORINFOEX and ScreenWinDisplay.
   // If we make it here, it means we have no displays and we should hand out the
   // default display.
   DCHECK_EQ(screen_win_displays_.size(), 0u);
   return ScreenWinDisplay();
 }
 
 // static
-float ScreenWin::GetScaleFactorForHWND(HWND hwnd) {
-  if (!g_screen_win_instance)
-    return ScreenWinDisplay().display().device_scale_factor();
-
-  DCHECK(hwnd);
-  HWND rootHwnd = g_screen_win_instance->GetRootWindow(hwnd);
-  ScreenWinDisplay screen_win_display =
-      g_screen_win_instance->GetScreenWinDisplayNearestHWND(rootHwnd);
-  return screen_win_display.display().device_scale_factor();
-}
-
-// static
 template <typename Getter, typename GetterType>
 ScreenWinDisplay ScreenWin::GetScreenWinDisplayVia(Getter getter,
                                                    GetterType value) {
   if (!g_screen_win_instance)
     return ScreenWinDisplay();
 
   return (g_screen_win_instance->*getter)(value);
 }
 
 void ScreenWin::RecordDisplayScaleFactors() const {
   std::vector<int> unique_scale_factors;
   for (const auto& screen_win_display : screen_win_displays_) {
     const float scale_factor =
         screen_win_display.display().device_scale_factor();
     // Multiply the reported value by 100 to display it as a percentage. Clamp
     // it so that if it's wildly out-of-band we won't send it to the backend.
     const int reported_scale = std::min(
         std::max(base::checked_cast<int>(scale_factor * 100), 0), 1000);
     if (std::find(unique_scale_factors.begin(), unique_scale_factors.end(),
                   reported_scale) == unique_scale_factors.end()) {
       unique_scale_factors.push_back(reported_scale);
       UMA_HISTOGRAM_SPARSE_SLOWLY("UI.DeviceScale", reported_scale);
     }
   }
 }
 
 }  // namespace win
 }  // namespace display