Orca reads neither Tor Browser nor Thunderbird if started after it

Originally created by @sajolida on #9260 (Redmine)

To reproduce on Tails 1.3.2:

1. Start Tails without networking.
2. Start Tor Browser.
3. Start Orca (Applications → Universal Access → Orca) and click Ok to enable default options.
4. Double-click on some text on the Tor Browser error page.
5. Nothing is read.

If you invert steps 2 and 3, the text in step 5 is read.

Feature Branch: bugfix/14752-a11y-enabled-after-tor-browser-is-started

Parent Task: #14522

Related issues

• Related to #9051 (closed)
• Related to #14752 (closed)
• Blocked by #14735 (closed)