Remove unused sequenced_worker_pool(_owner).h includes.

TBR=jochen@chromium.org

Bug: 667892
Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: If125f2f33081fb39184ad13594f187e8ec165148
Reviewed-on: https://chromium-review.googlesource.com/883767
Reviewed-by: Fran├žois Doray <fdoray@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Commit-Queue: Fran├žois Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#531935}
128 files changed