GitLab

Store base::TimeDeltas directly instead of converting to and from
TimeDeltaInternalType. This removes the use of To/FromInternalValue,
which are deprecated. No logic changes.

BUG=634507,b:116527691
TEST=Unit tests pass.

Change-Id: I7fe53e4c418651ff88da2a123c1ab943a590679b
Reviewed-on: https://chromium-review.googlesource.com/c/1340604Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Gabriel Marin <gmx@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609432}