Switch to equalIgnoringASCIICase throughout modules/accessibility

BUG=627682

Review-Url: https://codereview.chromium.org/2793913007
Cr-Commit-Position: refs/heads/master@{#461858}
bool AXObject::supportsARIAAttributes() const {
  return isLiveRegion() || supportsARIADragging() || supportsARIADropping() ||
         supportsARIAFlowTo() || supportsARIAOwns() ||
         hasAttribute(aria_labelAttr);
}

bool AXObject::supportsARIAAttributes() const {
  return isLiveRegion() || supportsARIADragging() || supportsARIADropping() ||
         supportsARIAFlowTo() || supportsARIAOwns() ||
         hasAttribute(aria_labelAttr);
}
