Revert of Don't post multiple task for executing blocked scripts.

Revert of Don't post multiple task for executing blocked scripts. (patchset #2 id:20001 of https://codereview.chromium.org/2609763002/ )

Reason for revert:
Regression in test for time to first meaningful paint: https://crbug.com/678584


Original issue's description:
> Don't post multiple task for executing blocked scripts.
> 
> We may post a lot of tasks for executing blocked scripts in the case
> where we insert multiple shadow trees each containing a style element.
> When we start parsing a style element, we mark it as blocking and
> unblock script execution after finishing parsing. Check if the previous
> task is active before posting.
> 
> Found while measuring performance for issue 603621.
> 
> BUG=603621
> 
> Committed: https://crrev.com/26cb3bdcd2a353402b78b716862567226317dff0
> Cr-Commit-Position: refs/heads/master@{#441110}

TBR=pmeenan@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=603621
Review-Url: https://codereview.chromium.org/2617763002
Cr-Commit-Position: refs/heads/master@{#441783}
Committed: https://chromium.googlesource.com/chromium/src/+/482c1f85b922eeec0b9525838baca4b884c27392

[rune, 2017-01-05 20:42:37]

The CQ bit was checked by rune@opera.com

[rune, 2017-01-05 20:42:38]

Created Revert of Don't post multiple task for executing blocked scripts.

[commit-bot: I haz the power, 2017-01-05 20:43:22]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-01-06 01:20:46]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1483648957956110, "parent_rev":
"59123b612a37738072b80870dfd18a7e8eaae241", "commit_rev":
"482c1f85b922eeec0b9525838baca4b884c27392"}

[commit-bot: I haz the power, 2017-01-06 01:21:17]

Description was changed from

==========
Revert of Don't post multiple task for executing blocked scripts. (patchset #2
id:20001 of https://codereview.chromium.org/2609763002/ )

Reason for revert:
Regression in test for time to first meaningful paint: https://crbug.com/678584


Original issue's description:
> Don't post multiple task for executing blocked scripts.
> 
> We may post a lot of tasks for executing blocked scripts in the case
> where we insert multiple shadow trees each containing a style element.
> When we start parsing a style element, we mark it as blocking and
> unblock script execution after finishing parsing. Check if the previous
> task is active before posting.
> 
> Found while measuring performance for issue 603621.
> 
> BUG=603621
> 
> Committed: https://crrev.com/26cb3bdcd2a353402b78b716862567226317dff0
> Cr-Commit-Position: refs/heads/master@{#441110}

TBR=pmeenan@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=603621
==========

to

==========
Revert of Don't post multiple task for executing blocked scripts. (patchset #2
id:20001 of https://codereview.chromium.org/2609763002/ )

Reason for revert:
Regression in test for time to first meaningful paint: https://crbug.com/678584


Original issue's description:
> Don't post multiple task for executing blocked scripts.
> 
> We may post a lot of tasks for executing blocked scripts in the case
> where we insert multiple shadow trees each containing a style element.
> When we start parsing a style element, we mark it as blocking and
> unblock script execution after finishing parsing. Check if the previous
> task is active before posting.
> 
> Found while measuring performance for issue 603621.
> 
> BUG=603621
> 
> Committed: https://crrev.com/26cb3bdcd2a353402b78b716862567226317dff0
> Cr-Commit-Position: refs/heads/master@{#441110}

TBR=pmeenan@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=603621

Review-Url: https://codereview.chromium.org/2617763002
Cr-Commit-Position: refs/heads/master@{#441783}
Committed:
https://chromium.googlesource.com/chromium/src/+/482c1f85b922eeec0b9525838bac...
==========

[commit-bot: I haz the power, 2017-01-06 01:21:19]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/482c1f85b922eeec0b9525838bac...