Revert "cc: Make scheduler run incoming frame after previous deadline."

This reverts commit d920c93c9c963460b835d19ca4540fe86640b19f.

Reason for revert:
Did not reduce input latency, retro frame CL wasn't even in the regression range

Original change's description:
> cc: Make scheduler run incoming frame after previous deadline.
> 
> When removing retro frames I made the incoming frame run the previous
> frame's deadline synchronously. This is believed to have regressed
> Event.Latency.OS.TOUCH_MOVED UMA metric. This CL changes the scheduler
> to queue the incoming frame and post a task for it after the previous
> deadline runs. This is a speculative fix for the UMA regression.
> 
> R=​enne
> BUG=702372
> 
> CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel
> 
> Change-Id: I0d8b0a5df90186b2158e4249540929b9b5ecc70b
> Reviewed-on: https://chromium-review.googlesource.com/478852
> Reviewed-by: enne <enne@chromium.org>
> Commit-Queue: Sunny Sachanandani <sunnyps@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#465769}

TBR=enne@chromium.org,sunnyps@chromium.org
# Not skipping CQ checks because original CL landed > 1 day ago.
BUG=702372
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel

Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I982f05fa5838500588767186bc1f28737682f0e9
Reviewed-on: https://chromium-review.googlesource.com/497293
Commit-Queue: Sunny Sachanandani <sunnyps@chromium.org>
Reviewed-by: Sunny Sachanandani <sunnyps@chromium.org>
Cr-Commit-Position: refs/heads/master@{#470807}

• cc/scheduler/begin_frame_tracker.cc[diff]
• cc/scheduler/begin_frame_tracker.h[diff]
• cc/scheduler/scheduler.cc[diff]
• cc/scheduler/scheduler.h[diff]
• cc/scheduler/scheduler_unittest.cc[diff]