change overlay scrollbar hover show to hover fade in

cc/trees/layer_tree_impl.cc

Index: cc/trees/layer_tree_impl.cc
diff --git a/cc/trees/layer_tree_impl.cc b/cc/trees/layer_tree_impl.cc
index 62e63b3ac94f16eadd6894016e0ef78d8858da03..90f0fa23afe5078ab3a726277dd357fcdb7f0f97 100644
--- a/cc/trees/layer_tree_impl.cc
+++ b/cc/trees/layer_tree_impl.cc
@@ -1469,11 +1469,11 @@ const gfx::Rect LayerTreeImpl::ViewportRectForTilePriority() const {
 std::unique_ptr<ScrollbarAnimationController>
 LayerTreeImpl::CreateScrollbarAnimationController(int scroll_layer_id) {
   DCHECK(!settings().scrollbar_fade_out_delay.is_zero());
-  DCHECK(!settings().scrollbar_fade_out_duration.is_zero());
+  DCHECK(!settings().scrollbar_fade_duration.is_zero());
   base::TimeDelta fade_out_delay = settings().scrollbar_fade_out_delay;
   base::TimeDelta fade_out_resize_delay =
       settings().scrollbar_fade_out_resize_delay;
-  base::TimeDelta fade_out_duration = settings().scrollbar_fade_out_duration;
+  base::TimeDelta fade_out_duration = settings().scrollbar_fade_duration;
   switch (settings().scrollbar_animator) {
     case LayerTreeSettings::ANDROID_OVERLAY: {
       return ScrollbarAnimationController::
@@ -1482,13 +1482,13 @@ LayerTreeImpl::CreateScrollbarAnimationController(int scroll_layer_id) {
               fade_out_resize_delay, fade_out_duration);
     }
     case LayerTreeSettings::AURA_OVERLAY: {
-      DCHECK(!settings().scrollbar_show_delay.is_zero());
-      base::TimeDelta show_delay = settings().scrollbar_show_delay;
+      DCHECK(!settings().scrollbar_fade_in_delay.is_zero());
+      base::TimeDelta fade_in_delay = settings().scrollbar_fade_in_delay;
       base::TimeDelta thinning_duration =
           settings().scrollbar_thinning_duration;
       return ScrollbarAnimationController::
           CreateScrollbarAnimationControllerAuraOverlay(
-              scroll_layer_id, layer_tree_host_impl_, show_delay,
+              scroll_layer_id, layer_tree_host_impl_, fade_in_delay,
               fade_out_delay, fade_out_resize_delay, fade_out_duration,
               thinning_duration);
     }