GitLab

BUG=461865
TEST:
1. enable physical keyboard autocorrect feature from IME settings from chrome-extension://jkghodnilhceideoidjikpgommlajknk/hmm_options.html?code=xkb:us::eng
2. type "waht" and wait for a grey triangle appear underneath "waht"
At this point, an IME window is created.
3. verify no default app icon appear in launcher for the IME window

Review URL: https://codereview.chromium.org/955983004

Cr-Commit-Position: refs/heads/master@{#318734}