During installation, only enqueue scripts when necessary

[flixos90]

The JS files enqueued during the installation routine are included in all the steps although they are not required in each one. This also creates some JS errors in the console.

[flixos90]

this patch only prints the scripts when they're needed

[ocean90]

user-profile.js?ver=4.4-beta4-35625-src-1447703485:202 Uncaught TypeError: Cannot read property 'prop' of undefined

[flixos90]

@ocean90 on what form did you find that error?

[ocean90]

Replying to flixos90:
Sry, that should have been a reply to your "This also creates some JS errors" note.

[ocean90]

Replying to ocean90:

This also creates some JS errors in the console.

user-profile.js?ver=4.4-beta4-35625-src-1447703485:202 Uncaught TypeError: Cannot read property 'prop' of undefined

The error is gone with [35649].

34700.diff​ doesn't work always, because the first step can be 0 or 1: // Deliberately fall through if we can't reach the translations API.

[flixos90]

Replying to ocean90:

34700.diff​ doesn't work always, because the first step can be 0 or 1: // Deliberately fall through if we can't reach the translations API.

34700.2.diff​ should fix it.

[ocean90]

@flixos90 Step 2 needs the user-profile script too because it also shows the display_setup_form() in case of errors.

Since wp_print_scripts() supports an array we can build a list of scripts to enqueue, see 34700.3.diff​.

[ocean90]

In 36176:

Install: Only enqueue scripts when necessary.

Props flixos90 for initial patch.
Fixes #34700.