Remove failure expectations for xhr tests that broke at chromium r267947

The patch that caused the change was reverted.

BUG=369730
TBR=loislo

Review URL: https://codereview.chromium.org/261273004

git-svn-id: svn://svn.chromium.org/blink/trunk@173327 bbb929c8-8fbe-4397-9dbb-9b2b20218538