This part:

  // Disable default drop interactions on the omnibox.
  // TODO(crbug.com/739903): Handle drop events once Chrome iOS is built with
  // the iOS 11 SDK.
  if (base::ios::IsRunningOnIOS11OrLater()) {
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
    SEL setInteractionsSelector = NSSelectorFromString(@"setInteractions:");
    if ([_omniBox respondsToSelector:setInteractionsSelector]) {
      [_omniBox performSelector:setInteractionsSelector withObject:@[]];
    }
#pragma clang diagnostic pop
  }