Ensure that extension resources are loaded with the correct scaling applied on Windows.

ui/base/layout.h

Index: ui/base/layout.h
diff --git a/ui/base/layout.h b/ui/base/layout.h
index 2ea39a289e2cb482e0d658629f232096dde4738d..6c09331571938fb719fda0a388c193ce9693b9a8 100644
--- a/ui/base/layout.h
+++ b/ui/base/layout.h
@@ -58,6 +58,13 @@ UI_BASE_EXPORT void SetSupportedScaleFactors(
 UI_BASE_EXPORT const std::vector<ScaleFactor>& GetSupportedScaleFactors();
 
 // Returns the float scale value for |scale_factor|.
+UI_BASE_EXPORT float GetImageScaleForScaleFactor(ScaleFactor scale_factor);
+
+// Returns the actual image scale to be used for the scale factor passed in.
+// For all platforms except Windows high dpi, this returns the value returned
+// by the GetImageScaleForScaleFactor function above.
+// For Windows with high dpi enabled it returns the dpi scale for the
+// display.
 UI_BASE_EXPORT float GetImageScale(ScaleFactor scale_factor);
 
 // Returns the supported ScaleFactor which most closely matches |scale|.