As per @TTO:
There are a few uses of Title::newFromURL left:
- MediaWiki core includes/MediaWiki.php. This one is going to be very difficult to get rid of, as it is on the critical path for almost all index.php requests (it's used to convert the title= parameter into $wgTitle). There are subtle effects here that may result in URL breakages.
- MediaWiki core includes/parser/CoreParserFunctions.php and Scribunto UrlLibrary. These seem to be used for handling user input (parameter to a parser function and a Lua function respectively) so are going to be more difficult to remove.
- Something in FlaggedRevs