Empty value in query should trigger safe search

When query in the search contains empty value, it should be
considered as a search query. Otherwise that is a possibility for safe
search escape.

Bug: chromium:787981
Test: Unit test.
Change-Id: I341b1821f9db5b8b0f8cc0aad9e5f714b706c5ce
Reviewed-on: https://chromium-review.googlesource.com/793714
Reviewed-by: Zhongyi Shi <zhongyi@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Commit-Queue: Igor <igorcov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#520483}
3 files changed