Update translation descriptions: alertDialogLabel, searchFieldLabel (#19234)

diff --git a/dev/tools/localizations_validator.dart b/dev/tools/localizations_validator.dart
index f73cfc1..11a6909 100644
--- a/dev/tools/localizations_validator.dart
+++ b/dev/tools/localizations_validator.dart
@@ -8,6 +8,7 @@
 /// Sanity checking of the @foo metadata in the English translations,
 /// material_en.arb.
 ///
+/// - For each foo, resource, there must be a corresponding @foo.
 /// - For each @foo resource, there must be a corresponding foo, except
 ///   for plurals, for which there must be a fooOther.
 /// - Each @foo resource must have a Map value with a String valued
@@ -23,6 +24,24 @@
   }
 
   final Map<String, dynamic> bundle = json.decode(file.readAsStringSync());
+
+  for (String resourceId in bundle.keys) {
+    if (resourceId.startsWith('@'))
+      continue;
+
+    if (bundle['@$resourceId'] != null)
+      continue;
+
+    bool checkPluralResource(String suffix) {
+      final int suffixIndex = resourceId.indexOf(suffix);
+      return suffixIndex != -1 && bundle['@${resourceId.substring(0, suffixIndex)}'] != null;
+    }
+    if (<String>['Zero', 'One', 'Two', 'Few', 'Many', 'Other'].any(checkPluralResource))
+      continue;
+
+    errorMessages.writeln('A value was not specified for @$resourceId');
+  }
+
   for (String atResourceId in bundle.keys) {
     if (!atResourceId.startsWith('@'))
       continue;
diff --git a/packages/flutter_localizations/lib/src/l10n/material_en.arb b/packages/flutter_localizations/lib/src/l10n/material_en.arb
index 23b1a14..5a6d308 100644
--- a/packages/flutter_localizations/lib/src/l10n/material_en.arb
+++ b/packages/flutter_localizations/lib/src/l10n/material_en.arb
@@ -197,12 +197,12 @@
   },
 
   "alertDialogLabel": "Alert",
-  "@dialogLabel": {
+  "@alertDialogLabel": {
     "description": "The audio announcement made when an AlertDialog is opened."
   },
 
   "searchFieldLabel": "Search",
-    "@dialogLabel": {
-      "description": "Label indicating that a text field is a search field. This will be used as a hint text in the text field."
-    }
+  "@searchFieldLabel": {
+    "description": "Label indicating that a text field is a search field. This will be used as a hint text in the text field."
+  }
 }