Let cached resources from file: schemes expire immediately
https://bugs.webkit.org/show_bug.cgi?id=113626

Reviewed by Brady Eidson

When a CachedResource was loaded from a file: URL, we would give it an
indefinite freshness lifetime. This means that we would continue to
serve a stale resource from the memory cache even if the file was
changed on disk. With the introduction of main resource caching, this
behavior broke at least one third-party WebKit app (see <rdar://problem/13313769>).

We should instead let file resources expire immediately. Modern
filesystems implement their own caching, so we should get good
performance for multiple reads of unmodified files without doing our
own caching.

* loader/cache/CachedResource.cpp:
(WebCore::CachedResource::freshnessLifetime): file: URLs should have a
0 freshness lifetime.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@147263 268f45cc-cd09-0410-ab3c-d52691b4dbfc