Switch to equalIgnoringASCIICase throughout modules/accessibility

BUG=627682

Review-Url: https://codereview.chromium.org/2793913007
Cr-Commit-Position: refs/heads/master@{#461858}
bool AXObject::hasAttribute(const QualifiedName& attribute) const {
  Node* elementNode = getNode();
  if (!elementNode)
    return false;

  if (!elementNode->isElementNode())
    return false;

  Element* element = toElement(elementNode);
  return element->fastHasAttribute(attribute);
}

bool AXObject::hasAttribute(const QualifiedName& attribute) const {
  Node* elementNode = getNode();
  if (!elementNode)
    return false;

  if (!elementNode->isElementNode())
    return false;

  Element* element = toElement(elementNode);
  return element->fastHasAttribute(attribute);
}
