service worker: Return true in IsServicificationEnabled().

The non-servicified code path is no longer supported. This is the
next step toward removing it.

This CL also removes some tests that only worked when
kServiceWorkerServicification was disabled. That code path can
no longer be taken, so the tests would fail.

The Signed Exchange tests were testing the combinations of
of ServiceWorkerServicification + NetworkService; this can
be removed now that we only need to test NetworkService on
or off, and there are dedicated bots on the CQ for that.

Bug: 926114
Change-Id: I5691139d045615dc463a8bf09f48186c5c6cd270
Reviewed-on: https://chromium-review.googlesource.com/c/1496268
Commit-Queue: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Auto-Submit: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#637227}
7 files changed