The code after the binary-search loop is unlikely to be reached,
but not actually UNREACHABLE(). Restore the "return 0" that was
there until a cleanup [1] removed it.

[1] crrev.com/c/507287/2/src/date.cc

Bug: chromium:767039
Change-Id: I9e007d3b7d693d4866ccc3e3cf2b71e78e9bd07f
Reviewed-on: https://chromium-review.googlesource.com/675755Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48117}