Adjust overlay scrollbar appearance.

ui/native_theme/overlay_scrollbar_constants_aura.h

Index: ui/native_theme/overlay_scrollbar_constants_aura.h
diff --git a/ui/native_theme/overlay_scrollbar_constants_aura.h b/ui/native_theme/overlay_scrollbar_constants_aura.h
index 65537995792dd13f5387a16e2a9c6a92f7ef2926..a6192d902249f49721dd6162b35e642024bc9f1e 100644
--- a/ui/native_theme/overlay_scrollbar_constants_aura.h
+++ b/ui/native_theme/overlay_scrollbar_constants_aura.h
@@ -10,10 +10,14 @@
 
 namespace ui {
 
-constexpr int kOverlayScrollbarThumbWidthNormal = 6;
-constexpr int kOverlayScrollbarThumbWidthHovered = 10;
+constexpr int kOverlayScrollbarStrokeWidth = 1;
 constexpr int kOverlayScrollbarThumbWidthPressed = 10;
 
+constexpr float kOverlayScrollbarThumbNormalAlpha = 0.5f;
+constexpr float kOverlayScrollbarThumbHoverAlpha = 0.7f;
+constexpr float kOverlayScrollbarStrokeNormalAlpha = 0.3f;
+constexpr float kOverlayScrollbarStrokeHoverAlpha = 0.5f;
+
 // kOverlayScrollbarShowDelay is only for the case where the mouse hovers near
 // the screen edge.
 constexpr base::TimeDelta kOverlayScrollbarShowDelay =