This cl introduces time checking in posix-like and mac systems.
base::Time::FromUTCExploded() and
base::Time::FromLocalExplode() can fail without returning
a proper error.

This fix does the following:
1) After calculations are done, create UTC or local time.
2) Convert UTC or local time back to exploded
3) Compare original exploded with converted one
4) If times are not equal, then return Time(0) indicating
an error.

Windows implementation already returns Time(0) on error.

BUG=601900

Review-Url: https://codereview.chromium.org/1988663002
Cr-Commit-Position: refs/heads/master@{#396638}