[blink] Remove work stealing

Work stealing is deprecated by script streaming on the task scheduler,
and broken anyway by ScriptResource-controlled script streaming.

Bug: 557466
Bug: 761977
Bug: 865098
Bug: 866868
Change-Id: Ie01d239b052ad7499e9884687bf95376a5cf6f9a
Reviewed-on: https://chromium-review.googlesource.com/c/1258168
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Reviewed-by: Daniel Vogelheim <vogelheim@chromium.org>
Reviewed-by: Hiroshige Hayashizaki <hiroshige@chromium.org>
Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#601921}
18 files changed