ResourceLoaderOptions also must be updated by updateRequestForAccessControl()

updateRequestForAccessControl() updates ResourceRequest for access
control, but ResourceLoaderOptions passed to FetchRequest also contains
configuration items that must be updated for access control.

This CL removes cookie handling code and iframe from the following
layout tests since they're testing user:pass but not cookie.
- access-control-preflight-credential-async.html
- access-control-preflight-credential-sync.html

A new test is added to check that no cookie is set in a preflight
request. This new test uses third-party-cookie-relaxing-iframe.html
which was loaded by the two tests but was not actually used.

Missing testRunner.setAlwaysAcceptCookies() calls are added to
third-party-cookie-relaxing-iframe.html.

BUG=377541
R=japhet

Review URL: https://codereview.chromium.org/312653002

git-svn-id: svn://svn.chromium.org/blink/trunk@175527 bbb929c8-8fbe-4397-9dbb-9b2b20218538