Revert of Optimize for TouchStart responsiveness

Revert of Optimize for TouchStart responsiveness (patchset #22 id:410001 of https://codereview.chromium.org/1320633002/ )

Reason for revert:
adds flaky test, causes other test to be flaky

BUG=530250
Original issue's description:
> Optimize for TouchStart responsiveness by modeling what the user is doing.
> We have come to realize that TouchStart responsiveness is really critical
> for a good user experience.
>
> This patch introduces a (initially very simple) system for modeling
> what the user is doing and predicting when they are likely to initiate a
> new gesture (taps are ignored).  We order task priority accordingly.
>
> In addition we extend the estimation of task cost to loading tasks
> which are often a significant source of jank.
>
> Load tasks can be very long (easily up to 1000ms). There is
> no good way to cooperatively schedule such a task but the
> least worst user experience seems to be if we get them out
> of the way as fast as possible.  Ideally we'd prioritize them
> but the order of IPC and LoadingTasks currently needs to
> be more or less in lockstep.  Instead we deprioritize compositor
> tasks inside a compositor gesture, which has the effect of
> prioritizing other work.
>
> Expected changes on Perf bots:
> 1. first_gesture_scroll_update_latency in smoothness.scrolling_tough_ad_cases
> should go down.  This should be highly user visible.
> 2. It's possible some compositor metrics such as queueing_durations
> may regress.  I don't expect this to be user visible.
>
> BUG=510398
> CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel
>
> Committed: https://crrev.com/464b1a5144ddb5135dad845aceb5b1f074221387
> Cr-Commit-Position: refs/heads/master@{#347937}

TBR=jochen@chromium.org,skyostil@chromium.org,alexclarke@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=510398
Committed: https://crrev.com/cb6de992880a9dfa6fe6efa00a096956f86a2ed9
Cr-Commit-Position: refs/heads/master@{#348440}

[jam, 2015-09-11 18:25:33]

Created Revert of Optimize for TouchStart responsiveness

[commit-bot: I haz the power, 2015-09-11 18:25:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1337993002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1337993002/1

[commit-bot: I haz the power, 2015-09-11 18:27:10]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-11 18:27:55]

Patchset 1 (id:??) landed as
https://crrev.com/cb6de992880a9dfa6fe6efa00a096956f86a2ed9
Cr-Commit-Position: refs/heads/master@{#348440}

[commit-bot: I haz the power, 2015-09-23 12:24:21]

Patchset 1 (id:??) landed as
https://crrev.com/cb6de992880a9dfa6fe6efa00a096956f86a2ed9
Cr-Commit-Position: refs/heads/master@{#348440}