Revert of Forward input and compositing tasks to the Blink scheduler

Revert of Forward input and compositing tasks to the Blink scheduler (patchset #21 id:400001 of https://codereview.chromium.org/363383002/)

Reason for revert:
suspecting it's causing the high rate of flakes in Instrumentation test ContentShellTest

BUG=411756
Original issue's description:
> Forward input and compositing tasks to the Blink scheduler
> 
> Instead of posting input and compositor tasks directly to the 
> main thread message loop, forward them to the Blink scheduler 
> so they can be prioritized over other tasks.
> 
> BUG=391005
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=290845
> 
> Committed: https://chromium.googlesource.com/chromium/src/+/68bab3290b45a8610ad875d3c92530477c16a948

TBR=jamesr@chromium.org,alexclarke@chromium.org,picksi@chromium.org,eseidel@chromium.org,skyostil@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=391005
Committed: https://crrev.com/410d6b1f38af9f17048ec2b2458615e26580b77c
Cr-Commit-Position: refs/heads/master@{#293686}

[jam, 2014-09-08 07:00:04]

Created Revert of Forward input and compositing tasks to the Blink scheduler

[commit-bot: I haz the power, 2014-09-08 07:14:45]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/jam@chromium.org/548253002/1

[commit-bot: I haz the power, 2014-09-08 07:22:24]

Committed patchset #1 (id:1) as 66f85d5405417e6ddd11e1b9be677062a2e3ae4f

[jam, 2014-09-08 14:36:47]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/548333002/ by jam@chromium.org.

The reason for reverting is: this didn't reduce flakiness.

[commit-bot: I haz the power, 2014-09-10 03:45:01]

Patchset 1 (id:??) landed as
https://crrev.com/410d6b1f38af9f17048ec2b2458615e26580b77c
Cr-Commit-Position: refs/heads/master@{#293686}