Migrate Dropdown to ScrollConfiguration2 (#8135)

Also use the word "dropdown" consistently over "drop down".

examples/flutter_gallery/lib/gallery/example_code.dart

@@ -55,7 +55,7 @@ new FlatButton(
 // Member variable holding value.
 String dropdownValue;
 
-// Drop down button with string values.
+// Dropdown button with string values.
 new DropdownButton<String>(
   value: dropdownValue,
   onChanged: (String newValue) {

packages/flutter/lib/material.dart

@@ -34,7 +34,7 @@ export 'src/material/divider.dart';
 export 'src/material/drawer.dart';
 export 'src/material/drawer_header.dart';
 export 'src/material/drawer_item.dart';
-export 'src/material/drop_down.dart';
+export 'src/material/dropdown.dart';
 export 'src/material/expand_icon.dart';
 export 'src/material/expansion_panel.dart';
 export 'src/material/flat_button.dart';

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

@@ -11,7 +11,7 @@ import 'package:flutter/widgets.dart';
 import 'checkbox.dart';
 import 'colors.dart';
 import 'debug.dart';
-import 'drop_down.dart';
+import 'dropdown.dart';
 import 'icon.dart';
 import 'icon_theme.dart';
 import 'icon_theme_data.dart';

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

@@ -79,23 +79,17 @@ class _DropdownMenuPainter extends CustomPainter {
 
 // Do not use the platform-specific default scroll configuration.
 // Dropdown menus should never overscroll or display an overscroll indicator.
-class _DropdownScrollConfigurationDelegate extends ScrollConfigurationDelegate {
-  const _DropdownScrollConfigurationDelegate(this._platform);
+class _DropdownScrollBehavior extends ScrollBehavior2 {
+  const _DropdownScrollBehavior();
 
   @override
-  TargetPlatform get platform => _platform;
-  final TargetPlatform _platform;
+  TargetPlatform getPlatform(BuildContext context) => Theme.of(context).platform;
 
   @override
-  ExtentScrollBehavior createScrollBehavior() => new OverscrollWhenScrollableBehavior(platform: platform);
+  Widget buildViewportChrome(BuildContext context, Widget child, AxisDirection axisDirection) => child;
 
   @override
-  Widget wrapScrollWidget(BuildContext context, Widget scrollWidget) {
-    return new ClampOverscrolls(edge: ScrollableEdge.both, child: scrollWidget);
-  }
-
-  @override
-  bool updateShouldNotify(ScrollConfigurationDelegate old) => platform != old.platform;
+  ScrollPhysics getScrollPhysics(BuildContext context) => const ClampingScrollPhysics();
 }
 
 class _DropdownMenu<T> extends StatefulWidget {
@@ -182,8 +176,8 @@ class _DropdownMenuState<T> extends State<_DropdownMenu<T>> {
         child: new Material(
           type: MaterialType.transparency,
           textStyle: route.style,
-          child: new ScrollConfiguration(
-            delegate: new _DropdownScrollConfigurationDelegate(Theme.of(context).platform),
+          child: new ScrollConfiguration2(
+            behavior: const _DropdownScrollBehavior(),
             child: new Scrollbar(
               child: new ListView(
                 controller: config.route.scrollController,
@@ -406,7 +400,7 @@ class DropdownButtonHideUnderline extends InheritedWidget {
 ///
 /// See also:
 ///
-///  * [DropdownButtonHideUnderline], which prevents its descendant drop down buttons
+///  * [DropdownButtonHideUnderline], which prevents its descendant dropdown buttons
 ///    from displaying their underlines.
 ///  * [RaisedButton], [FlatButton], ordinary buttons that trigger a single action.
 ///  * <https://material.google.com/components/buttons.html#buttons-dropdown-buttons>

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

@@ -13,7 +13,7 @@ import 'button_bar.dart';
 import 'card.dart';
 import 'data_table.dart';
 import 'data_table_source.dart';
-import 'drop_down.dart';
+import 'dropdown.dart';
 import 'icon.dart';
 import 'icon_button.dart';
 import 'icon_theme.dart';

packages/flutter/test/material/drop_down_test.dart → packages/flutter/test/material/dropdown_test.dart

@@ -59,7 +59,7 @@ bool sameGeometry(RenderBox box1, RenderBox box2) {
 
 
 void main() {
-  testWidgets('Drop down button control test', (WidgetTester tester) async {
+  testWidgets('Dropdown button control test', (WidgetTester tester) async {
     String value = 'one';
     void didChangeValue(String newValue) {
       value = newValue;
@@ -98,7 +98,7 @@ void main() {
     expect(value, equals('two'));
   });
 
-  testWidgets('Drop down button with no app', (WidgetTester tester) async {
+  testWidgets('Dropdown button with no app', (WidgetTester tester) async {
     String value = 'one';
     void didChangeValue(String newValue) {
       value = newValue;
@@ -151,7 +151,7 @@ void main() {
     expect(value, equals('two'));
   });
 
-  testWidgets('Drop down screen edges', (WidgetTester tester) async {
+  testWidgets('Dropdown screen edges', (WidgetTester tester) async {
     int value = 4;
     List<DropdownMenuItem<int>> items = <DropdownMenuItem<int>>[];
     for (int i = 0; i < 20; ++i)
@@ -203,7 +203,7 @@ void main() {
     await tester.pump(const Duration(seconds: 1)); // finish the menu animation
   });
 
-  testWidgets('Drop down button aligns selected menu item', (WidgetTester tester) async {
+  testWidgets('Dropdown button aligns selected menu item', (WidgetTester tester) async {
     Key buttonKey = new UniqueKey();
     String value = 'two';
 
@@ -237,7 +237,7 @@ void main() {
     checkSelectedItemTextGeometry(tester, 'two');
   });
 
-  testWidgets('Drop down button with isDense:true aligns selected menu item', (WidgetTester tester) async {
+  testWidgets('Dropdown button with isDense:true aligns selected menu item', (WidgetTester tester) async {
     Key buttonKey = new UniqueKey();
     String value = 'two';
 
@@ -290,7 +290,7 @@ void main() {
     RenderBox buttonBox = tester.renderObject(find.byKey(buttonKey));
     assert(buttonBox.attached);
 
-    // A DropDown button with a null value should be the same size as a
+    // A Dropdown button with a null value should be the same size as a
     // one with a non-null value.
     expect(buttonBox.localToGlobal(Point.origin), equals(buttonBoxNullValue.localToGlobal(Point.origin)));
     expect(buttonBox.size, equals(buttonBoxNullValue.size));
@@ -342,7 +342,7 @@ void main() {
     RenderBox buttonBox = tester.renderObject(find.byKey(buttonKey));
     assert(buttonBox.attached);
 
-    // A DropDown button with a null value and a hint should be the same size as a
+    // A Dropdown button with a null value and a hint should be the same size as a
     // one with a non-null value.
     expect(buttonBox.localToGlobal(Point.origin), equals(buttonBoxHintValue.localToGlobal(Point.origin)));
     expect(buttonBox.size, equals(buttonBoxHintValue.size));