Currently we have Time and TimeTicks sharing some methods. This patch
creates TimeBase, and makes Time and TimeTicks inherits from it, so that time
related classes won't have to implement common methods and it's easier to
introduce new time related classes.

BUG=v8:4990
LOG=n

Review-Url: https://codereview.chromium.org/1952843002
Cr-Commit-Position: refs/heads/master@{#36088}