Toolbar: Inaccessible link to about page if user can't access the dashboard

[ocean90]

wp_admin_bar_wp_menu() uses self_admin_url( 'about.php' ) to link to the about page even if a user can't access the dashboard of the current site.

Previously: #25162/[34122]

[ocean90]

See [18777] and [19166].

[afercia]

Tested a bit, looks good to me :) the only thing, when there's no link the icon doesn't change color on focus. That should be possible using some crazy CSS selector, something like:
#wpadminbar .menupop div[tabindex]:focus .ab-icon:before
I guess this should go in the custom color schemes too.

[ocean90]

@afercia Thanks for testing. Added the focus selector and a test in 37949.3.patch​.

[ocean90]

In 38660:

Toolbar: Update links to the about page if current user can't access the dashboard of the current site.

Add missing focus styling for menu items with an icon.

Fixes #37949.

[ocean90]

In 38661:

Toolbar: Don't run the test from [38660] for multisite.

See #37949.

[ocean90]

In 38663:

Toolbar: Split tests added in [38660] and add a multisite specific test.

See #37949.