Press This: there is no indication while saving

[azaozz]

That can result in some data loss especially with slow connection. The user may continue to type after clicking on Save draft, as is seems that "nothing happens".

[azaozz]

In 31875.patch:

• Show the spinner while saving a post.
• Don't redirect after saving a draft.
• Make the "unidentified error" message clearer.

[azaozz]

In 31992:

Press This:

• Show a spinner while saving a post.
• Do not redirect after saving a draft.
• Make the unidentified error message clearer.

Fixes #31875.

[helen]

In 31996:

Spinners: Toggle a class instead of show/hide.

Toggling spinners also now uses visibility instead of display, so that the space is always reserved and nothing moves around unexpectedly.

props cdog, MikeHansenMe, valendesigns.
fixes #22839. see #31875, #30725.