[orca-list] Flat review delay when reviewing page

[Edhoari Setiyoso <edhoari s gmail com>]

Hi,

When I review a html page using up/down arrow and pressing
numpad key for flat review, there is delay about 4 seconds before the
line is spoken.

Steps to reproduce:
- open any webpage  using firefox
- jump to a line using arrow key
- press numpad key (5 or 8)

Expected result:
- Orca immediately speaks current line

Actual result:
- There's delay around 4 seconds before orca speaks the line

System:
- Debian 9 Stretch x86_64
- Orca 3.25
- Firefox ESR 60


Best Regards 
-- 
Edhoari Setiyoso