[Extensions] Migrate ServiceWorker off behavior feature system

The FeatureSystem is failing to retrieve the behavior feature for service
workers, but the only reason this seems to be the case is because of
potential corruption in the JSON files (or the JSON parser otherwise choking).
For now, to reduce the crash rates, just migrate the service worker restriction
off the behavior feature system.


Review URL: https://codereview.chromium.org/1417563005

Cr-Commit-Position: refs/heads/master@{#356123}
(cherry picked from commit 2507a2fcd25244dadb7dfcc316426bee7b1df275)

Review URL: https://codereview.chromium.org/1417113004 .

Cr-Commit-Position: refs/branch-heads/2526@{#248}
Cr-Branched-From: cb947c0153db0ec02a8abbcb3ca086d88bf6006f-refs/heads/master@{#352221}
3 files changed