Switch to equalIgnoringASCIICase throughout modules/accessibility

BUG=627682

Review-Url: https://codereview.chromium.org/2793913007
Cr-Commit-Position: refs/heads/master@{#461858}
AXObject* AXObject::parentObjectIfExists() const {
  if (isDetached())
    return 0;

  if (m_parent)
    return m_parent;

  return computeParentIfExists();
}

AXObject* AXObject::parentObjectIfExists() const {
  if (isDetached())
    return 0;

  if (m_parent)
    return m_parent;

  return computeParentIfExists();
}
