Fix the DCHECK failures under zero state.

The DCHECK failures in components/omnibox code are caused by
not expecting empty input from zero state, and the case that there
should not be any default match for zero state suggestions.

Also fix another DCHECK failure caused by incorrect use of
UMA_HISTOGRAM_TIMES in recording OmniboxProvider latency code.

Bug: 925607, 920770
Change-Id: If643a564b94c8c429b4bb570593c35c5a2c36b6a
Reviewed-on: https://chromium-review.googlesource.com/c/1461343
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Commit-Queue: Jenny Zhang <jennyz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#631347}
3 files changed