Check CORS policy on redirect in TextTrackLoader

BUG=633885
TEST=new case in http/tests/security/text-track-crossorigin.html

Review-Url: https://codereview.chromium.org/2367583002
Cr-Commit-Position: refs/heads/master@{#421919}
(cherry picked from commit e99cc8e5a48ff4978d401c48a64f06649f647f3f)

Review URL: https://codereview.chromium.org/2400433002 .

Cr-Commit-Position: refs/branch-heads/2840@{#650}
Cr-Branched-From: 1ae106dbab4bddd85132d5b75c670794311f4c57-refs/heads/master@{#414607}
4 files changed