[desktop] default to shrink wrap on desktop platforms (#66754)

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

@@ -368,7 +368,18 @@ class ThemeData with Diagnosticable {
     textTheme = defaultTextTheme.merge(textTheme);
     primaryTextTheme = defaultPrimaryTextTheme.merge(primaryTextTheme);
     accentTextTheme = defaultAccentTextTheme.merge(accentTextTheme);
-    materialTapTargetSize ??= MaterialTapTargetSize.padded;
+    switch (platform) {
+      case TargetPlatform.android:
+      case TargetPlatform.fuchsia:
+      case TargetPlatform.iOS:
+        materialTapTargetSize ??= MaterialTapTargetSize.padded;
+        break;
+      case TargetPlatform.linux:
+      case TargetPlatform.macOS:
+      case TargetPlatform.windows:
+         materialTapTargetSize ??= MaterialTapTargetSize.shrinkWrap;
+        break;
+    }
     applyElevationOverlayColor ??= false;
 
     // Used as the default color (fill color) for RaisedButtons. Computing the

packages/flutter/test/material/theme_data_test.dart

@@ -96,11 +96,21 @@ void main() {
     expect(darkTheme.accentTextTheme.headline6.color, typography.white.headline6.color);
   });
 
-  test('Defaults to MaterialTapTargetBehavior.expanded', () {
-    final ThemeData themeData = ThemeData();
-
-    expect(themeData.materialTapTargetSize, MaterialTapTargetSize.padded);
-  });
+  testWidgets('Defaults to MaterialTapTargetBehavior.padded on mobile platforms and MaterialTapTargetBehavior.shrinkWrap on desktop', (WidgetTester tester) async {
+    final ThemeData themeData = ThemeData(platform: defaultTargetPlatform);
+    switch (defaultTargetPlatform) {
+      case TargetPlatform.android:
+      case TargetPlatform.fuchsia:
+      case TargetPlatform.iOS:
+        expect(themeData.materialTapTargetSize, MaterialTapTargetSize.padded);
+        break;
+      case TargetPlatform.linux:
+      case TargetPlatform.macOS:
+      case TargetPlatform.windows:
+        expect(themeData.materialTapTargetSize, MaterialTapTargetSize.shrinkWrap);
+        break;
+    }
+  }, variant: TargetPlatformVariant.all());
 
   test('Can control fontFamily default', () {
     final ThemeData themeData = ThemeData(

packages/flutter/test/widgets/sliver_fill_remaining_test.dart

@@ -25,6 +25,9 @@ void main() {
       Axis scrollDirection = Axis.vertical,
     }) {
     return MaterialApp(
+      theme:  ThemeData(
+        materialTapTargetSize: MaterialTapTargetSize.padded,
+      ),
       home: Scaffold(
         body: CustomScrollView(
           scrollDirection: scrollDirection,