Switch to equalIgnoringASCIICase throughout modules/accessibility

BUG=627682

Review-Url: https://codereview.chromium.org/2793913007
Cr-Commit-Position: refs/heads/master@{#461858}
static Element* siblingWithAriaRole(String role, Node* node) {
  Node* parent = node->parentNode();
  if (!parent)
    return 0;

  for (Element* sibling = ElementTraversal::firstChild(*parent); sibling;
        sibling = ElementTraversal::nextSibling(*sibling)) {
     const AtomicString& siblingAriaRole =
         AccessibleNode::getProperty(sibling, AOMStringProperty::kRole);
    if (equalIgnoringASCIICase(siblingAriaRole, role))
       return sibling;
   }
 
  return 0;
}

static Element* siblingWithAriaRole(String role, Node* node) {
  Node* parent = node->parentNode();
  if (!parent)
    return 0;

  for (Element* sibling = ElementTraversal::firstChild(*parent); sibling;
        sibling = ElementTraversal::nextSibling(*sibling)) {
     const AtomicString& siblingAriaRole =
         AccessibleNode::getProperty(sibling, AOMStringProperty::kRole);
    if (equalIgnoringCase(siblingAriaRole, role))
       return sibling;
   }
 
  return 0;
}
