Use Unthrottled instead of DOMManipulation in HTMLLinkElement/HTMLStyleElement

Use Unthrottled instead of DOMManipulation in HTMLLinkElement/HTMLStyleElement

The async tasks for HTMLLinkElement/HTMLStyleElement::dispatchPendingEvent()
are on the critical paths to show popup windows for extensions, but
the DOMManipulation task runner is throttled because the tasks are executed
before the popup windows become visible, causing delay in showing popups.

The scheduler is fixed by [1], but [1] is not merged to M-56.
This CL makes a mergeable workaround by using TaskType::Unthrottled for these
tasks to fix the issue on M-56.

[1] https://codereview.chromium.org/2620743002

BUG=649942
Review-Url: https://codereview.chromium.org/2596343002
Cr-Commit-Position: refs/heads/master@{#444559}
(cherry picked from commit 812f90689e6637a5a4f13151dba661464716e29e)

Review-Url: https://codereview.chromium.org/2641263002 .
Cr-Commit-Position: refs/branch-heads/2924@{#809}
Cr-Branched-From: 3a87aecc31cd1ffe751dd72c04e5a96a1fc8108a-refs/heads/master@{#433059}
Committed: https://chromium.googlesource.com/chromium/src/+/b64349d476d54ffbc86da51fc51ec1d75413fd7c

[hiroshige, 2017-01-19 23:20:25]

Description was changed from

==========
Use Unthrottled instead of DOMManipulation in HTMLLinkElement/HTMLStyleElement

The async tasks for HTMLLinkElement/HTMLStyleElement::dispatchPendingEvent()
are on the critical paths to show popup windows for extensions, but
the DOMManipulation task runner is throttled because the tasks are executed
before the popup windows become visible, causing delay in showing popups.

The scheduler is fixed by [1], but [1] is not merged to M-56.
This CL makes a mergeable workaround by using TaskType::Unthrottled for these
tasks to fix the issue on M-56.

[1] https://codereview.chromium.org/2620743002

BUG=649942

Review-Url: https://codereview.chromium.org/2596343002
Cr-Commit-Position: refs/heads/master@{#444559}
(cherry picked from commit 812f90689e6637a5a4f13151dba661464716e29e)
==========

to

==========
Use Unthrottled instead of DOMManipulation in HTMLLinkElement/HTMLStyleElement

The async tasks for HTMLLinkElement/HTMLStyleElement::dispatchPendingEvent()
are on the critical paths to show popup windows for extensions, but
the DOMManipulation task runner is throttled because the tasks are executed
before the popup windows become visible, causing delay in showing popups.

The scheduler is fixed by [1], but [1] is not merged to M-56.
This CL makes a mergeable workaround by using TaskType::Unthrottled for these
tasks to fix the issue on M-56.

[1] https://codereview.chromium.org/2620743002

BUG=649942

Review-Url: https://codereview.chromium.org/2596343002
Cr-Commit-Position: refs/heads/master@{#444559}
(cherry picked from commit 812f90689e6637a5a4f13151dba661464716e29e)

Review-Url: https://codereview.chromium.org/2641263002 .
Cr-Commit-Position: refs/branch-heads/2924@{#809}
Cr-Branched-From:
3a87aecc31cd1ffe751dd72c04e5a96a1fc8108a-refs/heads/master@{#433059}
Committed:
https://chromium.googlesource.com/chromium/src/+/b64349d476d54ffbc86da51fc51e...
==========

[hiroshige, 2017-01-19 23:20:26]

Committed patchset #1 (id:1) manually as
b64349d476d54ffbc86da51fc51ec1d75413fd7c.