global-font-lock-mode-check-buffers: What does it do?

[raman@google.com]

I see that global-font-lock-mode-check-buffers is present in
post-command-hook  -- that function appears to get defined
automagically in font-core.el - at least that's where find-function
jumps when asked about that function. It's present in the .elc file,
but not in font-core.el so I guess it's getting generated through a
macro call -- haven't found where though.
The function has no doc string.

Am looking to see what it does while trying to debug a problem with
Emacspeak's voice-lock in Info mode buffers.

Background:

emacspeak attaches property 'personality to match  Emacs' font-locking
to produce audio-formatted output. It works everywhere but has stopped
working in Info buffers:

1. When I open an Info node for the first time, voice-lock is applied
correctly and I hear all the voice changes.

2. Subsequently -- if I perform any command in that displayed info
buffer -- including C-n for moving by line, the personality properties
disappear -- the face properties are present.

3. If I move to another node that hasn't been displayed, I hear the
effects of voice-lock -- returning to the previously displayed node
shows the voice properties to be still missing.

Am suspecting post-command-hook as   a possible place where something
might be going wrong since the voice properties disappear the moment I
interact with the Info buffer.
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