Worker: Move WebServiceWorkerNetworkProviderForSharedWorker to its own file

Before this CL, WebServiceWorkerNetworkProviderForSharedWorker is defined in
embedded_shared_worker_stub.cc.

This CL moves WebServiceWorkerNetworkProviderForSharedWorker into its own file,
and renames it to WebServiceWorkerNetworkProviderImplForWorker so that it's
reusable for dedicated workers(*).

(*) Currently, dedicated workers use parent document's
WebServiceWorkerNetworkProviderForFrame(**). After PlzDedicatedWorker is
implemented, dedicated workers have their own network provider, that is,
WebServiceWorkerNetworkProviderImplForWorker.

(**) WebServiceWorkerNetworkProviderForFrame will be renamed to
WebServiceWorkerNetworkProvider*Impl*ForFrame in a follow-up CL to clarify it's
the implementation of WebServiceWorkerNetworkProvider for Frame.

Bug: 906991
Change-Id: I8c7ebd60aff2e20f4082a44eef43338ce23584ba
Reviewed-on: https://chromium-review.googlesource.com/c/1391659
Commit-Queue: Hiroki Nakagawa <nhiroki@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#620637}
4 files changed