contrib/tweaks/visual/overlay-scrollbar-opacity.patch

## This patch sets a minimum opacity for scrollbars.  
# 
# I use the OverlayScrollbar feature flag, and enjoy the aesthetic except for
# the fact that the scrollbar disappears completely.  Being able to see the bar
# slightly helps to visulize your position on the page as well as letting you
# know where to move your mouse should you go reaching for it.  
#
# I use 0.15 here, but you can adjust that to your liking.  

--- a/cc/input/scrollbar_animation_controller.cc
+++ b/cc/input/scrollbar_animation_controller.cc
@@ -364,6 +364,8 @@ void ScrollbarAnimationController::Show(
 }
 
 void ScrollbarAnimationController::ApplyOpacityToScrollbars(float opacity) {
+  if (opacity < 0.15f)
+    opacity = 0.15f;
   for (ScrollbarLayerImplBase* scrollbar : Scrollbars()) {
     DCHECK(scrollbar->is_overlay_scrollbar());
     float effective_opacity = scrollbar->CanScrollOrientation() ? opacity : 0;