Move AllowedByNosniff to platform/loader

To cleanup the logic around AllowedByNosniff in
WorkerClassicScriptLoader, [1] will move AllowedByNosniff
option to FetchClientSettingsObject (in platform/loader).
As a preparation, this CL moves
AllowedByNosniff to platform/loader.

This shouldn't change the behavior.

[1] https://chromium-review.googlesource.com/1351929

Bug: 880027
Change-Id: I348d97820cc37b843f3e7b5c5a19bcbc4d01e790
Reviewed-on: https://chromium-review.googlesource.com/c/1351873
Commit-Queue: Hiroshige Hayashizaki <hiroshige@chromium.org>
Reviewed-by: Mike West <mkwst@chromium.org>
Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Cr-Commit-Position: refs/heads/master@{#613879}
15 files changed