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..690335aabc8c02e3791bda48643ff5409f366066 100644
--- a/ui/base/layout.h
+++ b/ui/base/layout.h
@@ -57,7 +57,8 @@ UI_BASE_EXPORT void SetSupportedScaleFactors(
 // platform, in ascending order.
 UI_BASE_EXPORT const std::vector<ScaleFactor>& GetSupportedScaleFactors();
 
-// Returns the float scale value for |scale_factor|.
+// Returns the actual image scale to be used for the scale factor passed in.
+// On Windows high dpi, this returns the dpi scale for the display.
 UI_BASE_EXPORT float GetImageScale(ScaleFactor scale_factor);
 
 // Returns the supported ScaleFactor which most closely matches |scale|.
@@ -77,6 +78,9 @@ UI_BASE_EXPORT bool IsScaleFactorSupported(ScaleFactor scale_factor);
 // Finding the closest match is inefficient and shouldn't be done frequently.
 UI_BASE_EXPORT ScaleFactor FindClosestScaleFactorUnsafe(float scale);
 
+// Returns the image scale for the scale factor passed in.
+UI_BASE_EXPORT float GetScaleForScaleFactor(ScaleFactor scale_factor);
+
 namespace test {
 // Class which changes the value of GetSupportedScaleFactors() to
 // |new_scale_factors| for the duration of its lifetime.