Move ServiceWorkerServicification to blink::features.

It's sometimes useful for Blink to define features instead of putting them in
//content. In this case, ServiceWorkerServicification.

Follow-up to r568796 <https://chromium-review.googlesource.com/1107435>.

Change-Id: Ia174481414f2ceeb2f463307436170628da84346
Reviewed-on: https://chromium-review.googlesource.com/1108237
Commit-Queue: Kinuko Yasuda <[email protected]>
Reviewed-by: Kinuko Yasuda <[email protected]>
Cr-Commit-Position: refs/heads/master@{#569209}
19 files changed