[OnionSoup] Move SWFetchRequest::GetCMFLF into content::SWUtils

This CL is a preparation for removing content::SWFetchRequest.

SWFetchRequest::GetCacheModeFromLoadFlags() is moved into
content/common/service_worker/service_worker_utils.{h,cc}.

BUG=789854

Change-Id: I4cac6d5469b42384843c73a2157955c39ad4d7a3
Reviewed-on: https://chromium-review.googlesource.com/c/1270516
Commit-Queue: Richard Li <richard.li@intel.com>
Reviewed-by: Makoto Shimazu <shimazu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#598251}
7 files changed