Add feature to keep service worker thread isolate in foreground mode.

Bug: 945505
Change-Id: I70e28253fb65dba437924ef761e6a136fea3f3bd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1539194
Reviewed-by: Brian White <bcwhite@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#654209}
4 files changed