[chrome:omnibox] clear previous outputs on making a new request.

A line was accidentally left out when moving code in the previous cl [1] resulting in outputs from the previous query not being cleared when making a new query when the `Show incomplete results` option was enabled.

[1] https://chromium-review.googlesource.com/c/chromium/src/+/1252324

Change-Id: I12f8465898171badff2e6c4f69fcbcaf121f680b
Bug: 891303
Reviewed-on: https://chromium-review.googlesource.com/c/1264815
Reviewed-by: Tommy Li <tommycli@chromium.org>
Commit-Queue: manuk hovanesian <manukh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#597156}
1 file changed