Gardening: add NeedsRebaseline for form-validation-reportValidity.html on XP.
Gardening: add NeedsRebaseline for form-validation-reportValidity.html on XP.

The last rebaseline wasn't quite correct:
https://chromium.googlesource.com/chromium/src/+/9fd8fea953f56baf1d4adcf4e275b2619542fc26%5E%21/#F0

BUG=490511
TBR=kojii@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/1465183008

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#361651}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk