Implement overlay scrollbar fade out for non-composited scrollers.

third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.cpp

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 149 matching lines @@
 
   WebThemeEngine::Part part = WebThemeEngine::PartScrollbarHorizontalThumb;
   if (scrollbar.orientation() == VerticalScrollbar)
     part = WebThemeEngine::PartScrollbarVerticalThumb;
 
   blink::WebThemeEngine::ExtraParams params;
   params.scrollbarThumb.scrollbarTheme =
       static_cast<WebScrollbarOverlayColorTheme>(
           scrollbar.getScrollbarOverlayColorTheme());
 
+  if (!scrollbar.enabled())

[skobes, 2016/11/02 21:02:43]

Move this up next to the rest of the "state = " logic.

[bokan, 2016/11/02 22:41:57]

Done.

+    state = WebThemeEngine::StateDisabled;
+
   Platform::current()->themeEngine()->paint(canvas, part, state, WebRect(rect),
                                             &params);
 }
 
 ScrollbarPart ScrollbarThemeOverlay::hitTest(
     const ScrollbarThemeClient& scrollbar,
     const IntPoint& position) {
   if (m_allowHitTest == DisallowHitTest)
     return NoPart;
 
-  return ScrollbarTheme::hitTest(scrollbar, position);
+  ScrollbarPart part = ScrollbarTheme::hitTest(scrollbar, position);
+  if (part != ThumbPart)
+    return NoPart;
+
+  return ThumbPart;
 }
 
 ScrollbarThemeOverlay& ScrollbarThemeOverlay::mobileTheme() {
   static ScrollbarThemeOverlay* theme;
   if (!theme) {
     WebThemeEngine::ScrollbarStyle style = {3, 3, 0x80808080};  // default style
     if (Platform::current()->themeEngine()) {
       Platform::current()->themeEngine()->getOverlayScrollbarStyle(&style);
     }
     theme = new ScrollbarThemeOverlay(
         style.thumbThickness, style.scrollbarMargin,
         ScrollbarThemeOverlay::DisallowHitTest, Color(style.color));
   }
   return *theme;
 }
 
 }  // namespace blink