[HttpCache] LOAD_ONLY_FROM_CACHE should not imply LOAD_PREFERRING_CACHE
LOAD_ONLY_FROM_CACHE won't go to the network, but it also skips the check to
see if the cache entry is valid. Some clients need to load only from cache,
but also ensure that the returned entry is valid. To accomplish this, this CL:
1) Renames LOAD_PREFERRING_CACHE -> LOAD_SKIP_CACHE_VALIDATION
2) Changes LOAD_ONLY_FROM_CACHE to check entry validity by default
3) Changes all existing uses of LOAD_ONLY_FROM_CACHE to also add
LOAD_SKIP_CACHE_VALIDATION, keeping the old behavior
BUG=652649
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_site_isolation
Review-Url: https://codereview.chromium.org/2398613002
Cr-Commit-Position: refs/heads/master@{#428026}
17 files changed
