Nuke TickTime::UseFakeClock.

Removes the global simulated time that affects (or breaks) following
tests in the same binary and replaces it with SimulatedClock.

BUG=webrtc:5318
R=mflodman@webrtc.org

Review URL: https://codereview.webrtc.org/1512853002 .

Cr-Original-Commit-Position: refs/heads/master@{#10947}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: d3c944755ec546f46d5bdd84bff359fe6c4639e9
15 files changed