Fix isDense default for DropdownButtonFormField (#47160)

packages/flutter/lib/src/material/dropdown.dart

@@ -1402,7 +1402,7 @@ class DropdownButtonFormField<T> extends FormField<T> {
     Color iconDisabledColor,
     Color iconEnabledColor,
     double iconSize = 24.0,
-    bool isDense = false,
+    bool isDense = true,
     bool isExpanded = false,
     double itemHeight,
   }) : assert(items == null || items.isEmpty || value == null ||

packages/flutter/test/material/dropdown_form_field_test.dart

@@ -13,6 +13,10 @@ import '../rendering/mock_canvas.dart';
 
 const List<String> menuItems = <String>['one', 'two', 'three', 'four'];
 final ValueChanged<String> onChanged = (_) { };
+final Type dropdownButtonType = DropdownButton<String>(
+  onChanged: (_) { },
+  items: const <DropdownMenuItem<String>>[],
+).runtimeType;
 
 Finder _iconRichText(Key iconKey) {
   return find.descendant(
@@ -31,7 +35,7 @@ Widget buildFormFrame({
   Color iconDisabledColor,
   Color iconEnabledColor,
   double iconSize = 24.0,
-  bool isDense = false,
+  bool isDense = true,
   bool isExpanded = false,
   Widget hint,
   Widget disabledHint,
@@ -227,7 +231,6 @@ void main() {
       buildFormFrame(
         buttonKey: buttonKey,
         value: value,
-        isDense: true,
         onChanged: onChanged,
       ),
     );
@@ -262,6 +265,35 @@ void main() {
     }
   });
 
+  testWidgets('DropdownButtonFormField.isDense is true by default', (WidgetTester tester) async {
+    // Regression test for https://github.com/flutter/flutter/issues/46844
+    final Key buttonKey = UniqueKey();
+    const String value = 'two';
+
+    await tester.pumpWidget(
+      TestApp(
+        textDirection: TextDirection.ltr,
+        child: Material(
+          child: DropdownButtonFormField<String>(
+            key: buttonKey,
+            value: value,
+            onChanged: onChanged,
+            items: menuItems.map<DropdownMenuItem<String>>((String item) {
+              return DropdownMenuItem<String>(
+                key: ValueKey<String>(item),
+                value: item,
+                child: Text(item, key: ValueKey<String>(item + 'Text')),
+              );
+            }).toList(),
+          ),
+        ),
+      ),
+    );
+
+    final RenderBox box = tester.renderObject<RenderBox>(find.byType(dropdownButtonType));
+    expect(box.size.height, 24.0);
+  });
+
   testWidgets('DropdownButtonFormField - custom text style', (WidgetTester tester) async {
     const String value = 'foo';
     final UniqueKey itemKey = UniqueKey();