Revert of Remove IdleNotification call in the main thread of foreground tab.

Revert of Remove IdleNotification call in the main thread of foreground tab. (patchset #1 id:1 of https://codereview.chromium.org/1320073005/ )

Reason for revert:
Reverting because of regression  in v8.top_25_smooth benchmark (crbug.com/530391)

Original issue's description:
> Remove IdleNotification call in the main thread of foreground tab.
> 
> V8 posts idle tasks explicitly.
> 
> BUG=chromium:490559
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=201977

TBR=rmcilroy@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:490559
Committed: https://crrev.com/d9054a96215d745e2b3e730ff67dbf0236f1b8ba
git-svn-id: svn://svn.chromium.org/blink/trunk@202123 bbb929c8-8fbe-4397-9dbb-9b2b20218538

[ulan, 2015-09-11 09:24:56]

Created Revert of Remove IdleNotification call in the main thread of foreground
tab.

[commit-bot: I haz the power, 2015-09-11 09:25:07]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1336923003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1336923003/1

[haraken, 2015-09-11 09:25:23]

LGTM

[commit-bot: I haz the power, 2015-09-11 09:25:43]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=202123

[commit-bot: I haz the power, 2015-09-23 12:20:46]

Patchset 1 (id:??) landed as
https://crrev.com/d9054a96215d745e2b3e730ff67dbf0236f1b8ba