High CPU usage and text cursor flickering when password field is focused in firefox 68

Issue

• In Firefox 68 on GNOME desktop, if a text cursor is moved to a password field, the cursor flickers and CPU usage of gnome-shell, firefox, and ibus-daemon increases suddenly, and sometimes it is difficult to input a password. This issue is likely to occur when both "English (US)" and "Japanese (Kana Kanji)" are configured as input sources.