Merge pull request #20548 from RudyLu/settings/Bug1024695-waitFor_keyboard_settings_frame

Bug 1024695 - Intermittent keyboard_settings_test.js |
r=evanxd.
(cherry picked from commit 7b4665c7521a50e52b2053445d2a93c42a1f4ebd)
a=test-only