[deep link] Add more explanation for cross checking. (#8020)

* wording

1

* Update validation_details_view.dart

* wording

packages/devtools_app/lib/src/screens/deep_link_validation/validation_details_view.dart

@@ -578,6 +578,7 @@ class _CrossCheckTable extends StatelessWidget {
  final missingIos = hasIosAasaFile && !linkData.os.contains(PlatformOS.ios);
  final missingAndroid =
  hasAndroidAssetLinksFile && !linkData.os.contains(PlatformOS.android);
+ if (!missingIos && !missingAndroid) return const SizedBox.shrink();
 
  final theme = Theme.of(context);
  final domainMissing = Text(
@@ -602,14 +603,30 @@ class _CrossCheckTable extends StatelessWidget {
  os: PlatformOS.android,
  checkName: 'Manifest file',
  status: domainMissing,
- children: const <Widget>[],
+ children: const <Widget>[
+ Padding(
+ padding: EdgeInsets.symmetric(horizontal: defaultSpacing),
+ child: Text(
+ 'This domain has an Asset link json file but it\'s missing in the android manifest file. '
+ 'If you want to set up deep linking for Android, you need to add this domain '
+ 'to your AndroidManifest.xml file.'),
+ ),
+ ],
  ),
  if (missingIos)
  _CheckExpansionTile(
  os: PlatformOS.ios,
  checkName: 'Settings',
  status: domainMissing,
- children: const <Widget>[],
+ children: const <Widget>[
+ Padding(
+ padding: EdgeInsets.symmetric(horizontal: defaultSpacing),
+ child: Text(
+ 'This domain has an AASA file but it\'s missing in local settings. '
+ 'If you want to set up deep linking for iOS, you need to add this domain '
+ 'to your info.Plist file.'),
+ ),
+ ],
  ),
  ],
  );