Remove FetchContext::CreateResourceLoadingTaskRunner

It's used only used in (Frame|Worker)FetchContext::CreateURLLoader, so
move the function to each implementation.

Bug: 914739
Change-Id: If275b26c91e7e6cd911afe429ea7da27460eeeab
Reviewed-on: https://chromium-review.googlesource.com/c/1399687
Reviewed-by: Alexander Timin <altimin@chromium.org>
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#620944}
4 files changed