Switch to equalIgnoringASCIICase throughout modules/accessibility

BUG=627682

Review-Url: https://codereview.chromium.org/2793913007
Cr-Commit-Position: refs/heads/master@{#461858}
 bool AXTableCell::computeAccessibilityIsIgnored(
    IgnoredReasons* ignoredReasons) const {
  AXObjectInclusion decision = defaultObjectInclusion(ignoredReasons);
  if (decision == IncludeObject)
    return false;
  if (decision == IgnoreObject)
    return true;

  if (!isTableCell())
    return AXLayoutObject::computeAccessibilityIsIgnored(ignoredReasons);

  return false;
}

 bool AXTableCell::computeAccessibilityIsIgnored(
    IgnoredReasons* ignoredReasons) const {
  AXObjectInclusion decision = defaultObjectInclusion(ignoredReasons);
  if (decision == IncludeObject)
    return false;
  if (decision == IgnoreObject)
    return true;

  if (!isTableCell())
    return AXLayoutObject::computeAccessibilityIsIgnored(ignoredReasons);

  return false;
}
