Retire fast/dom/Window/window-early-properties-xhr.html flaky expectation.
Retire fast/dom/Window/window-early-properties-xhr.html flaky expectation.

No evidence of it being slow on Windows any longer.

R=
BUG=409713
NOTRY=true

Review URL: https://codereview.chromium.org/643593002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@183449 bbb929c8-8fbe-4397-9dbb-9b2b20218538

primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs