[Merge to M57] Scheduler: Enqueue non-JS-timer tasks into the unthrottled task runner

[Merge to M57] Scheduler: Enqueue non-JS-timer tasks into the unthrottled task runner

We found throttling some of non-JS-timer tasks may break existing web pages,
so this CL tentatively makes them unthrottled.

In addition, this CL switches a task type for PostMessageTimer from
TaskType::Timer to TaskType::PostedMessage because the timer is used only for
performing postMessage() and actually not used as a JS timer.

BUG=684947
Review-Url: https://codereview.chromium.org/2669883003
Cr-Commit-Position: refs/heads/master@{#448173}
(cherry picked from commit 04055dd2786e27cde8d210b68e7a726fab6d0c42)

Review-Url: https://codereview.chromium.org/2679083002 .
Cr-Commit-Position: refs/branch-heads/2987@{#359}
Cr-Branched-From: ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed: https://chromium.googlesource.com/chromium/src/+/91f69c5c73122c96f0690490d09b176526bf975b

[nhiroki, 2017-02-07 11:05:33]

Description was changed from

==========
[Merge to M57] Scheduler: Enqueue non-JS-timer tasks into the unthrottled task
runner

We found throttling some of non-JS-timer tasks may break existing web pages,
so this CL tentatively makes them unthrottled.

In addition, this CL switches a task type for PostMessageTimer from
TaskType::Timer to TaskType::PostedMessage because the timer is used only for
performing postMessage() and actually not used as a JS timer.

BUG=684947

Review-Url: https://codereview.chromium.org/2669883003
Cr-Commit-Position: refs/heads/master@{#448173}
(cherry picked from commit 04055dd2786e27cde8d210b68e7a726fab6d0c42)
==========

to

==========
[Merge to M57] Scheduler: Enqueue non-JS-timer tasks into the unthrottled task
runner

We found throttling some of non-JS-timer tasks may break existing web pages,
so this CL tentatively makes them unthrottled.

In addition, this CL switches a task type for PostMessageTimer from
TaskType::Timer to TaskType::PostedMessage because the timer is used only for
performing postMessage() and actually not used as a JS timer.

BUG=684947

Review-Url: https://codereview.chromium.org/2669883003
Cr-Commit-Position: refs/heads/master@{#448173}
(cherry picked from commit 04055dd2786e27cde8d210b68e7a726fab6d0c42)

Review-Url: https://codereview.chromium.org/2679083002 .
Cr-Commit-Position: refs/branch-heads/2987@{#359}
Cr-Branched-From:
ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed:
https://chromium.googlesource.com/chromium/src/+/91f69c5c73122c96f0690490d09b...
==========

[nhiroki, 2017-02-07 11:05:34]

Committed patchset #1 (id:1) manually as
91f69c5c73122c96f0690490d09b176526bf975b.