Ensure correct state for resources fetched via fetch???Resource.

This CL asserts that resources fetched via the various
'ResourceFetcher::fetch???Resource' methods have a frame-type of 'none'
and sets the request context as appropriate.

BUG=390497

Review URL: https://codereview.chromium.org/390833002

git-svn-id: svn://svn.chromium.org/blink/trunk@178260 bbb929c8-8fbe-4397-9dbb-9b2b20218538