8945e0112f
The root cause was that we crawled the tree to mark anyone who depended on the updated theme dirty _after_ we crawled it to rebuild it. Thus, if anyone was already marked dirty when the process started, then got marked clean by the first (rebuild) walk, then got marked dirty again by the notification, they'd be clean when they got the notification, despite already being in the dirty list, which would cause an assertion. Also IconTheme didn't have an operator==, so it was independently too aggressive about updates.