Remove title attributes from Walker_Nav_Menu

[sabernhardt]

Removes redundant tooltips from Walker_Nav_Menu::start_el()

Trac 51299

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[sabernhardt]

51299.2.diff compared the title attribute against the item title, filtered only by the_title. If I had a good reason to compare before nav_menu_item_title three years ago, I did not explain it on the ticket, and I do not understand that decision today.

This PR now checks the title attribute after both the_title and nav_menu_item_title filters, and it still removes redundant tooltips before the nav_menu_link_attributes hook.

[joedolson]

The value that is rendered is the version that's passed through both filters, and if we want to prevent duplicate values, we should generally pass through both filters.

However, Twenty Seventeen inserts an icon using the nav_menu_item_title filter. Other plugins and themes may do similar things. That will result in a difference in value, even though the accessible name may be unchanged.

Because of that, I'm wondering if we actually want to get those as two separate variables and compare against both of them, ignoring the title attribute if it matches either value.

[sabernhardt]

Twenty Seventeen inserts an icon using the nav_menu_item_title filter.

That might be why I moved the comparison earlier in 51299.2.diff.

I'm wondering if we actually want to get those as two separate variables and compare against both of them, ignoring the title attribute if it matches either value.

Maybe. Switching trim() to wp_strip_all_tags() could be another option.

[joedolson]

wp_strip_all_tags() would work for the twenty seventeen example, but there are potentially other cases it wouldn't work for. I'm imagining cases where people are inserting file extensions, screen reader text strings, where they're changing link texts dynamically based on the current user or logged in state, etc.

I think that the most valid use case of this attribute is where it definitely provides something other than the link text, and that shouldn't generally overlap with text that might be shown visually. I'd rather err in the direction of removing more title attributes than less.

[joedolson]

In r59177