Remove usage of SequencedWorkerPool in DhcpProxyScriptFetcherWin.

Bug: 667892
Change-Id: Ic76fa46f26f798f23819dd36600ccfde2a7025c0
Reviewed-on: https://chromium-review.googlesource.com/881273
Commit-Queue: François Doray <fdoray@chromium.org>
Reviewed-by: Eric Roman <eroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#538105}
4 files changed