Replaces the stock scrollbars with 6px-wide versions that have rounded ends, no arrows, and a background that attempts to blend with the page. The bars are a medium grey, and nearly black on hover.
Scrollbars for UI elements like drop-downs are not affected, but iframes and scrolling divs usually are - and with backgrounds that truly blend with the page.
This extension is extremely lightweight - just a vew lines of CSS, and roughly equivalent to restoring support for Custom.css userstyles without any interface to edit the new CSS file. No more expertise is needed to tweak this extension than to edit the Custom.css file Chrome no longer supports.