change overlay scrollbar hover show to hover fade in

cc/trees/layer_tree_settings.h

Index: cc/trees/layer_tree_settings.h
diff --git a/cc/trees/layer_tree_settings.h b/cc/trees/layer_tree_settings.h
index 996d6279fec606adbca0a193de0e998d22f46250..a39c4e4954da9ff1b1c0f577b5f4114b9e0627be 100644
--- a/cc/trees/layer_tree_settings.h
+++ b/cc/trees/layer_tree_settings.h
@@ -50,10 +50,9 @@ class CC_EXPORT LayerTreeSettings {
     AURA_OVERLAY,
   };
   ScrollbarAnimator scrollbar_animator = NO_ANIMATOR;
-  base::TimeDelta scrollbar_show_delay;
-  base::TimeDelta scrollbar_fade_out_delay;
+  base::TimeDelta scrollbar_fade_delay;
   base::TimeDelta scrollbar_fade_out_resize_delay;
-  base::TimeDelta scrollbar_fade_out_duration;
+  base::TimeDelta scrollbar_fade_duration;
   base::TimeDelta scrollbar_thinning_duration;
   SkColor solid_color_scrollbar_color = SK_ColorWHITE;
   bool timeout_and_draw_when_animation_checkerboards = true;