persistentsize rule does not work

[yuukibarns]

windowrule = persistentsize,floating:1

No thing changed, floating windows are still small at startup and need manual adjustment every time.

By the way, I wonder how can you track the windows by their initialClass and initialTitle, for there can be windows with different size but share the same parent. For example, Anki. And even for those with different initialTitle from their parents, their size aren't all remembered (Save File of browsers do, but Anki's Add does not)

[yuukibarns]

Related #9422

[yuukibarns]

Okay, I think the current implementation has two problems:

1. windowrule float should be used with persistentsize so that floating windows are opened in the last size stored in the memory.
2. I think we should store sizes of windows caches or config files or whatever, so that sizes can be persistent across boots.

I think I've fixed the first problem by this PR #10212, but I need further instruction on the second.