Use TimeDelta in media controls/PiP

Straightforward double -> TimeDelta conversion. Names of constants have
been changed to remove any unit (like "...Seconds") - often replaced by
"...Duration". "Trans" was also expanded to "Transition" in a few
places.

Bug: 763980
Change-Id: I1b193ecf338245c5873f002c0cfcd1b679b345d7
Reviewed-on: https://chromium-review.googlesource.com/1127782
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Commit-Queue: Fredrik Söderquist <fs@opera.com>
Cr-Commit-Position: refs/heads/master@{#572971}
4 files changed