Switch to equalIgnoringASCIICase throughout modules/accessibility

BUG=627682

Review-Url: https://codereview.chromium.org/2793913007
Cr-Commit-Position: refs/heads/master@{#461858}
bool AXLayoutObject::liveRegionAtomic() const {
  if (getAttribute(aria_atomicAttr).isEmpty() &&
      (roleValue() == AlertRole || roleValue() == StatusRole)) {
    return true;
  }
  return elementAttributeValue(aria_atomicAttr);
}

bool AXLayoutObject::liveRegionAtomic() const {
  if (getAttribute(aria_atomicAttr).isEmpty() &&
      (roleValue() == AlertRole || roleValue() == StatusRole)) {
    return true;
  }
  return elementAttributeValue(aria_atomicAttr);
}
