Fix Jumplist favicons to have high resolution in HDPI Windows displays

ui/gfx/favicon_size.h

Index: ui/gfx/favicon_size.h
diff --git a/ui/gfx/favicon_size.h b/ui/gfx/favicon_size.h
index ad51a9bdb005b93e7e0f3efadc0ab8b3f22e7920..53051f80eee399e4bb9188a2b5fb05dcf00475a7 100644
--- a/ui/gfx/favicon_size.h
+++ b/ui/gfx/favicon_size.h
@@ -12,6 +12,9 @@ namespace gfx {
 // Size (along each axis) of the favicon.
 GFX_EXPORT extern const int kFaviconSize;
 
+// Size (along each axis) of the favicon for HDPI displays.
+GFX_EXPORT extern const int kHdpiFaviconSize;
+
 // If the width or height is bigger than the favicon size, a new width/height
 // is calculated and returned in width/height that maintains the aspect
 // ratio of the supplied values.