Don't categorize back/forward continuations as reloads.

If a reload turns into a loadHistoryItem with a reload-like cachePolicy and
that reload then generates an error, still categorize the navigation as a
back/forward navigation. The check for a ReloadIgnoringCacheData cachePolicy
was happening before and miscategorizing those navigations as reloads.

BUG=348918

Review URL: https://codereview.chromium.org/188063003

git-svn-id: svn://svn.chromium.org/blink/trunk@168839 bbb929c8-8fbe-4397-9dbb-9b2b20218538