Bug 1702970 [wpt PR 28365] - Revert "Move ImageDecoder API decoding over to sequenced...

Bug 1702970 [wpt PR 28365] - Revert "Move ImageDecoder API decoding over to sequenced worker thread.", a=testonly

Automatic update from web-platform-tests
Revert "Move ImageDecoder API decoding over to sequenced worker thread."

This reverts commit a5f3d67b351ca099af4c447c9d91b6d445bf60d9.

Reason for revert:

Findit (https://goo.gl/kROfz5) identified CL at revision 869115 as the
culprit for failures in the build cycles as shown on:
https://analysis.chromium.org/waterfall/culprit?key=ag9zfmZpbmRpdC1mb3ItbWVyRAsSDVdmU3VzcGVjdGVkQ0wiMWNocm9taXVtL2E1ZjNkNjdiMzUxY2EwOTlhZjRjNDQ3YzlkOTFiNmQ0NDViZjYwZDkM

Sample Failed Build: https://ci.chromium.org/b/8850801698879608080

Sample Failed Step: webkit_unit_tests

Original change's description:
> Move ImageDecoder API decoding over to sequenced worker thread.
>
> This moves the actual image decoding into a new ImageDecoderCore
> class which can be used with WTF::SequenceBound to decode images
> on a sequenced worker pool.
>
> This follows the WebCodecs processing model where decoding is not
> supposed to occur on the main thread.
>
> Fixed: 1182435
>
> Change-Id: I22a89d9242110fb17010f1fd178bcb5fc59fb5a1
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2799173
> Reviewed-by: Dan Sanders <sandersd@chromium.org>
> Reviewed-by: Yuta Kitamura <yutak@chromium.org>
> Reviewed-by: Chrome Cunningham <chcunningham@chromium.org>
> Commit-Queue: Dale Curtis <dalecurtis@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#869115}

Change-Id: Ieca8deee310ddae92074f9cd7f7ed420a7c52d80
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2804678
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Fabian Sommer <fabiansommer@chromium.org>
Owners-Override: Fabian Sommer <fabiansommer@chromium.org>
Auto-Submit: Fabian Sommer <fabiansommer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#869136}

--

wpt-commits: 9c622c8a2ba9d058442fe46d75ade96d17b611b1
wpt-pr: 28365