From the commit log message: "Extensions are a much better way of doing this."
This is not to be confused with developer mode on Chromebooks, which does make each boot very annoying.
Extensions exist which make this significaly friendly to all involved, such as Stylish.
Right, there should be a basic UI setting to do load an specified stylesheet as the default.
That doesn't excuse removing basic functionality expected of a user agent out of the core and requiring an extensionto provide it at all, especially since that requires reducing security (by extending the number of trusted parties) to use that basic function.
"We didn't expose this basic function well enough by default" is a good reason to improve the UX related to the function, its not a good excuse to make the situation even worse.
CSS stylesheets are nicely portable and should work in any (well, most) browser.
In general, a browser agnostic solution is preferable to a browser-specific solution, if they have the same functionality....
Stylesheets are also arguably much simpler to write, and far more concise for their problem space.
Maybe if user stylesheets didn't exist, you could say it isn't worth the effort to implement them, as javascript extensions are a "good enough" solution for a somewhat rare circumstance. But actually removing the existing, standardized, portable, feature seems a tad bizarre... [It's hard to believe it required much code.]
This is a great point. If a user went through the trouble of creating custom styles to make certain sites accessible, browsers should follow a standardized way of managing these styles. Just like a user can import their bookmarks when changing browsers, styles should be handled similarly.
It might be extra effort for browsers to handle this uncommon feature, but it is the right thing to do, especially for users facing accessibility issues.