Move WebScopedVirtualTimePauser creation to FrameFetchContext

In order to remove FetchContext::FrameSchduler, this CL moves
WebScopedVirtualTimePauser creation code from
ResourceFetcher::StartLoad to FrameFetchContext::PrepareRequest.

WorkerFetchContext is not affected because
WorkerFetchContext::GetFrameScheduler always returns null.

Bug: 914739
Change-Id: I9fbdf9809272ab0c0497b816cd8fe3ff029a45ae
Reviewed-on: https://chromium-review.googlesource.com/c/1415237
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Reviewed-by: Hiroshige Hayashizaki <hiroshige@chromium.org>
Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Cr-Commit-Position: refs/heads/master@{#624145}
10 files changed