Move CachedMetadata and CrossOriginAccessControl to fetch/ from loader/

These classes are used from fetch/ and aren't tied to frame loading,
which loader/ module is responsible for.

TEST=none
BUG=280939
R=japhet@chromium.org,abarth@chromium.org

Review URL: https://chromiumcodereview.appspot.com/23565005

git-svn-id: svn://svn.chromium.org/blink/trunk@157195 bbb929c8-8fbe-4397-9dbb-9b2b20218538