make some widgets const (#9477)

examples/flutter_gallery/lib/demo/contacts_demo.dart

@@ -128,15 +128,15 @@ class ContactsDemoState extends State<ContactsDemo> {
                     });
                   },
                   itemBuilder: (BuildContext context) => <PopupMenuItem<AppBarBehavior>>[
-                    new PopupMenuItem<AppBarBehavior>(
+                    const PopupMenuItem<AppBarBehavior>(
                       value: AppBarBehavior.normal,
                       child: const Text('App bar scrolls away')
                     ),
-                    new PopupMenuItem<AppBarBehavior>(
+                    const PopupMenuItem<AppBarBehavior>(
                       value: AppBarBehavior.pinned,
                       child: const Text('App bar stays put')
                     ),
-                    new PopupMenuItem<AppBarBehavior>(
+                    const PopupMenuItem<AppBarBehavior>(
                       value: AppBarBehavior.floating,
                       child: const Text('App bar floats')
                     ),

examples/flutter_gallery/lib/demo/material/bottom_navigation_demo.dart

@@ -192,11 +192,11 @@ class _BottomNavigationDemoState extends State<BottomNavigationDemo>
               });
             },
             itemBuilder: (BuildContext context) => <PopupMenuItem<BottomNavigationBarType>>[
-              new PopupMenuItem<BottomNavigationBarType>(
+              const PopupMenuItem<BottomNavigationBarType>(
                 value: BottomNavigationBarType.fixed,
                 child: const Text('Fixed'),
               ),
-              new PopupMenuItem<BottomNavigationBarType>(
+              const PopupMenuItem<BottomNavigationBarType>(
                 value: BottomNavigationBarType.shifting,
                 child: const Text('Shifting'),
               )

examples/flutter_gallery/lib/demo/material/grid_list_demo.dart

@@ -317,15 +317,15 @@ class GridListDemoState extends State<GridListDemo> {
           new PopupMenuButton<GridDemoTileStyle>(
             onSelected: changeTileStyle,
             itemBuilder: (BuildContext context) => <PopupMenuItem<GridDemoTileStyle>>[
-              new PopupMenuItem<GridDemoTileStyle>(
+              const PopupMenuItem<GridDemoTileStyle>(
                 value: GridDemoTileStyle.imageOnly,
                 child: const Text('Image only'),
               ),
-              new PopupMenuItem<GridDemoTileStyle>(
+              const PopupMenuItem<GridDemoTileStyle>(
                 value: GridDemoTileStyle.oneLine,
                 child: const Text('One line'),
               ),
-              new PopupMenuItem<GridDemoTileStyle>(
+              const PopupMenuItem<GridDemoTileStyle>(
                 value: GridDemoTileStyle.twoLine,
                 child: const Text('Two line'),
               ),

examples/flutter_gallery/lib/demo/material/leave_behind_demo.dart

@@ -137,11 +137,11 @@ class LeaveBehindDemoState extends State<LeaveBehindDemo> {
           new PopupMenuButton<LeaveBehindDemoAction>(
             onSelected: handleDemoAction,
             itemBuilder: (BuildContext context) => <PopupMenuEntry<LeaveBehindDemoAction>>[
-              new PopupMenuItem<LeaveBehindDemoAction>(
+              const PopupMenuItem<LeaveBehindDemoAction>(
                 value: LeaveBehindDemoAction.reset,
                 child: const Text('Reset the list')
               ),
-              new PopupMenuDivider(), // ignore: list_element_type_not_assignable, https://github.com/flutter/flutter/issues/5771
+              const PopupMenuDivider(), // ignore: list_element_type_not_assignable, https://github.com/flutter/flutter/issues/5771
               new CheckedPopupMenuItem<LeaveBehindDemoAction>(
                 value: LeaveBehindDemoAction.horizontalSwipe,
                 checked: _dismissDirection == DismissDirection.horizontal,

examples/flutter_gallery/lib/demo/material/menu_demo.dart

@@ -67,15 +67,15 @@ class MenuDemoState extends State<MenuDemo> {
           new PopupMenuButton<String>(
             onSelected: showMenuSelection,
             itemBuilder: (BuildContext context) => <PopupMenuItem<String>>[
-              new PopupMenuItem<String>(
+              const PopupMenuItem<String>(
                 value: 'Toolbar menu',
                 child: const Text('Toolbar menu')
               ),
-              new PopupMenuItem<String>(
+              const PopupMenuItem<String>(
                 value: 'Right here',
                 child: const Text('Right here')
               ),
-              new PopupMenuItem<String>(
+              const PopupMenuItem<String>(
                 value: 'Hooray!',
                 child: const Text('Hooray!')
               ),
@@ -99,7 +99,7 @@ class MenuDemoState extends State<MenuDemo> {
                   value: _simpleValue1,
                   child: const Text('Context menu item one')
                 ),
-                new PopupMenuItem<String>(
+                const PopupMenuItem<String>(
                   enabled: false,
                   child: const Text('A disabled menu item')
                 ),
@@ -140,7 +140,7 @@ class MenuDemoState extends State<MenuDemo> {
                     title: const Text('Get link')
                   )
                 ),
-                new PopupMenuDivider(), // ignore: list_element_type_not_assignable, https://github.com/flutter/flutter/issues/5771
+                const PopupMenuDivider(), // ignore: list_element_type_not_assignable, https://github.com/flutter/flutter/issues/5771
                 new PopupMenuItem<String>(
                   value: 'Remove',
                   child: new ListTile(

examples/flutter_gallery/lib/demo/material/progress_indicator_demo.dart

@@ -63,17 +63,17 @@ class _ProgressIndicatorDemoState extends State<ProgressIndicatorDemo> with Sing
 
   Widget _buildIndicators(BuildContext context, Widget child) {
     final List<Widget> indicators = <Widget>[
-      new SizedBox(
+      const SizedBox(
         width: 200.0,
-        child: new LinearProgressIndicator()
+        child: const LinearProgressIndicator()
       ),
-      new LinearProgressIndicator(),
-      new LinearProgressIndicator(),
+      const LinearProgressIndicator(),
+      const LinearProgressIndicator(),
       new LinearProgressIndicator(value: _animation.value),
       new Row(
         mainAxisAlignment: MainAxisAlignment.spaceEvenly,
         children: <Widget>[
-          new CircularProgressIndicator(),
+          const CircularProgressIndicator(),
           new SizedBox(
               width: 20.0,
               height: 20.0,

examples/flutter_gallery/lib/demo/material/scrollable_tabs_demo.dart

@@ -64,15 +64,15 @@ class ScrollableTabsDemoState extends State<ScrollableTabsDemo> with SingleTicke
           new PopupMenuButton<TabsDemoStyle>(
             onSelected: changeDemoStyle,
             itemBuilder: (BuildContext context) => <PopupMenuItem<TabsDemoStyle>>[
-              new PopupMenuItem<TabsDemoStyle>(
+              const PopupMenuItem<TabsDemoStyle>(
                 value: TabsDemoStyle.iconsAndText,
                 child: const Text('Icons and text')
               ),
-              new PopupMenuItem<TabsDemoStyle>(
+              const PopupMenuItem<TabsDemoStyle>(
                 value: TabsDemoStyle.iconsOnly,
                 child: const Text('Icons only')
               ),
-              new PopupMenuItem<TabsDemoStyle>(
+              const PopupMenuItem<TabsDemoStyle>(
                 value: TabsDemoStyle.textOnly,
                 child: const Text('Text only')
               ),

examples/flutter_gallery/lib/demo/material/selection_controls_demo.dart

@@ -174,8 +174,8 @@ class _SelectionControlsDemoState extends State<SelectionControlsDemo> {
             }
           ),
           // Disabled switches
-          new Switch(value: true, onChanged: null),
-          new Switch(value: false, onChanged: null)
+          const Switch(value: true, onChanged: null),
+          const Switch(value: false, onChanged: null)
         ],
       ),
     );

examples/flutter_gallery/lib/demo/shrine/shrine_page.dart

@@ -113,15 +113,15 @@ class ShrinePageState extends State<ShrinePage> {
           ),
           new PopupMenuButton<ShrineAction>(
             itemBuilder: (BuildContext context) => <PopupMenuItem<ShrineAction>>[
-              new PopupMenuItem<ShrineAction>(
+              const PopupMenuItem<ShrineAction>(
                 value: ShrineAction.sortByPrice,
                 child: const Text('Sort by price')
               ),
-              new PopupMenuItem<ShrineAction>(
+              const PopupMenuItem<ShrineAction>(
                 value: ShrineAction.sortByProduct,
                 child: const Text('Sort by product')
               ),
-              new PopupMenuItem<ShrineAction>(
+              const PopupMenuItem<ShrineAction>(
                 value: ShrineAction.emptyCart,
                 child: const Text('Empty shopping cart')
               )

examples/flutter_gallery/lib/gallery/demo.dart

@@ -128,8 +128,8 @@ class FullScreenCodeDialogState extends State<FullScreenCodeDialog> {
 
     Widget body;
     if (_exampleCode == null) {
-      body = new Center(
-        child: new CircularProgressIndicator()
+      body = const Center(
+        child: const CircularProgressIndicator()
       );
     } else {
       body = new SingleChildScrollView(

examples/flutter_gallery/lib/gallery/example_code.dart

@@ -192,7 +192,7 @@ new Switch(
 // Create a disabled switch.
 // Switches are disabled when onChanged isn't
 // specified or null.
-new Switch(value: false, onChanged: null);
+const Switch(value: false, onChanged: null);
 // END
   }
 }

examples/stocks/lib/stock_home.dart

@@ -209,15 +209,15 @@ class StockHomeState extends State<StockHome> {
               checked: _autorefresh,
               child: const Text('Autorefresh'),
             ),
-            new PopupMenuItem<_StockMenuItem>(
+            const PopupMenuItem<_StockMenuItem>(
               value: _StockMenuItem.refresh,
               child: const Text('Refresh'),
             ),
-            new PopupMenuItem<_StockMenuItem>(
+            const PopupMenuItem<_StockMenuItem>(
               value: _StockMenuItem.speedUp,
               child: const Text('Increase animation speed'),
             ),
-            new PopupMenuItem<_StockMenuItem>(
+            const PopupMenuItem<_StockMenuItem>(
               value: _StockMenuItem.speedDown,
               child: const Text('Decrease animation speed'),
             ),

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

@@ -434,10 +434,10 @@ class _LicensePageState extends State<LicensePage> {
     ];
     contents.addAll(_licenses);
     if (!_loaded) {
-      contents.add(new Padding(
+      contents.add(const Padding(
         padding: const EdgeInsets.symmetric(vertical: 24.0),
-        child: new Center(
-          child: new CircularProgressIndicator()
+        child: const Center(
+          child: const CircularProgressIndicator()
         )
       ));
     }

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

@@ -484,7 +484,7 @@ class _AppBarState extends State<AppBar> {
 }
 
 class _FloatingAppBar extends StatefulWidget {
-  _FloatingAppBar({ Key key, this.child }) : super(key: key);
+  const _FloatingAppBar({ Key key, this.child }) : super(key: key);
 
   final Widget child;
 

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

@@ -243,13 +243,13 @@ class PaginatedDataTableState extends State<PaginatedDataTable> {
     final List<DataCell> cells = widget.columns.map<DataCell>((DataColumn column) {
       if (!column.numeric) {
         haveProgressIndicator = true;
-        return new DataCell(new CircularProgressIndicator());
+        return const DataCell(const CircularProgressIndicator());
       }
       return DataCell.empty;
     }).toList();
     if (!haveProgressIndicator) {
       haveProgressIndicator = true;
-      cells[0] = new DataCell(new CircularProgressIndicator());
+      cells[0] = const DataCell(const CircularProgressIndicator());
     }
     return new DataRow.byIndex(
       index: index,

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

@@ -76,7 +76,7 @@ class PopupMenuDivider extends PopupMenuEntry<dynamic> {
   /// Creates a horizontal divider for a popup menu.
   ///
   /// By default, the divider has a height of 16.0 logical pixels.
-  PopupMenuDivider({ Key key, this.height: 16.0 }) : super(key: key);
+  const PopupMenuDivider({ Key key, this.height: 16.0 }) : super(key: key);
 
   @override
   final double height;
@@ -111,7 +111,7 @@ class PopupMenuItem<T> extends PopupMenuEntry<T> {
   /// Creates an item for a popup menu.
   ///
   /// By default, the item is enabled.
-  PopupMenuItem({
+  const PopupMenuItem({
     Key key,
     this.value,
     this.enabled: true,
@@ -195,7 +195,7 @@ class CheckedPopupMenuItem<T> extends PopupMenuItem<T> {
   /// Creates a popup menu item with a checkmark.
   ///
   /// By default, the menu item is enabled but unchecked.
-  CheckedPopupMenuItem({
+  const CheckedPopupMenuItem({
     Key key,
     T value,
     this.checked: false,
@@ -252,7 +252,7 @@ class _CheckedPopupMenuItemState<T> extends _PopupMenuItemState<CheckedPopupMenu
 }
 
 class _PopupMenu<T> extends StatelessWidget {
-  _PopupMenu({
+  const _PopupMenu({
     Key key,
     this.route
   }) : super(key: key);

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

@@ -30,7 +30,7 @@ abstract class ProgressIndicator extends StatefulWidget {
   /// The [value] argument can be either null (corresponding to an indeterminate
   /// progress indcator) or non-null (corresponding to a determinate progress
   /// indicator). See [value] for details.
-  ProgressIndicator({
+  const ProgressIndicator({
     Key key,
     this.value,
     this.backgroundColor,
@@ -137,7 +137,7 @@ class LinearProgressIndicator extends ProgressIndicator {
   /// The [value] argument can be either null (corresponding to an indeterminate
   /// progress indcator) or non-null (corresponding to a determinate progress
   /// indicator). See [value] for details.
-  LinearProgressIndicator({
+  const LinearProgressIndicator({
     Key key,
     double value
   }) : super(key: key, value: value);
@@ -278,7 +278,7 @@ class CircularProgressIndicator extends ProgressIndicator {
   /// The [value] argument can be either null (corresponding to an indeterminate
   /// progress indcator) or non-null (corresponding to a determinate progress
   /// indicator). See [value] for details.
-  CircularProgressIndicator({
+  const CircularProgressIndicator({
     Key key,
     double value,
     Color backgroundColor,
@@ -438,7 +438,7 @@ class RefreshProgressIndicator extends CircularProgressIndicator {
   ///
   /// Rather than creating a refresh progress indicator directly, consider using
   /// a [RefreshIndicator] together with a [Scrollable] widget.
-  RefreshProgressIndicator({
+  const RefreshProgressIndicator({
     Key key,
     double value,
     Color backgroundColor,

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

@@ -42,7 +42,7 @@ class Switch extends StatefulWidget {
   ///
   /// * [value] determines this switch is on or off.
   /// * [onChanged] is called when the user toggles with switch on or off.
-  Switch({
+  const Switch({
     Key key,
     @required this.value,
     @required this.onChanged,
@@ -137,7 +137,7 @@ class _SwitchState extends State<Switch> with TickerProviderStateMixin {
 }
 
 class _SwitchRenderObjectWidget extends LeafRenderObjectWidget {
-  _SwitchRenderObjectWidget({
+  const _SwitchRenderObjectWidget({
     Key key,
     this.value,
     this.activeColor,

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

@@ -8,7 +8,7 @@ import 'package:flutter/material.dart';
 import 'debug.dart';
 
 class _AccountPictures extends StatelessWidget {
-  _AccountPictures({
+  const _AccountPictures({
     Key key,
     this.currentAccountPicture,
     this.otherAccountsPictures,
@@ -49,7 +49,7 @@ class _AccountPictures extends StatelessWidget {
 }
 
 class _AccountDetails extends StatelessWidget {
-  _AccountDetails({
+  const _AccountDetails({
     Key key,
     @required this.accountName,
     @required this.accountEmail,
@@ -132,7 +132,7 @@ class UserAccountsDrawerHeader extends StatefulWidget {
   /// Creates a material design drawer header.
   ///
   /// Requires one of its ancestors to be a [Material] widget.
-  UserAccountsDrawerHeader({
+  const UserAccountsDrawerHeader({
     Key key,
     this.decoration,
     this.margin: const EdgeInsets.only(bottom: 8.0),

packages/flutter/test/material/popup_menu_test.dart

@@ -26,7 +26,7 @@ void main() {
                   },
                   itemBuilder: (BuildContext context) {
                     return <PopupMenuItem<int>>[
-                      new PopupMenuItem<int>(
+                      const PopupMenuItem<int>(
                         value: 1,
                         child: const Text('One')
                       )

packages/flutter/test/material/progress_indicator_test.dart

@@ -13,10 +13,10 @@ void main() {
 
   testWidgets('LinearProgressIndicator(value: 0.0) can be constructed', (WidgetTester tester) async {
     await tester.pumpWidget(
-      new Center(
-        child: new SizedBox(
+      const Center(
+        child: const SizedBox(
           width: 200.0,
-          child: new LinearProgressIndicator(value: 0.0)
+          child: const LinearProgressIndicator(value: 0.0)
         )
       )
     );
@@ -24,10 +24,10 @@ void main() {
 
   testWidgets('LinearProgressIndicator(value: null) can be constructed', (WidgetTester tester) async {
     await tester.pumpWidget(
-      new Center(
-        child: new SizedBox(
+      const Center(
+        child: const SizedBox(
           width: 200.0,
-          child: new LinearProgressIndicator(value: null)
+          child: const LinearProgressIndicator(value: null)
         )
       )
     );
@@ -35,24 +35,24 @@ void main() {
 
   testWidgets('CircularProgressIndicator(value: 0.0) can be constructed', (WidgetTester tester) async {
     await tester.pumpWidget(
-      new Center(
-        child: new CircularProgressIndicator(value: 0.0)
+      const Center(
+        child: const CircularProgressIndicator(value: 0.0)
       )
     );
   });
 
   testWidgets('CircularProgressIndicator(value: null) can be constructed', (WidgetTester tester) async {
     await tester.pumpWidget(
-      new Center(
-        child: new CircularProgressIndicator(value: null)
+      const Center(
+        child: const CircularProgressIndicator(value: null)
       )
     );
   });
 
   testWidgets('LinearProgressIndicator causes a repaint when it changes', (WidgetTester tester) async {
-    await tester.pumpWidget(new ListView(children: <Widget>[new LinearProgressIndicator(value: 0.0)]));
+    await tester.pumpWidget(new ListView(children: <Widget>[const LinearProgressIndicator(value: 0.0)]));
     final List<Layer> layers1 = tester.layers;
-    await tester.pumpWidget(new ListView(children: <Widget>[new LinearProgressIndicator(value: 0.5)]));
+    await tester.pumpWidget(new ListView(children: <Widget>[const LinearProgressIndicator(value: 0.5)]));
     final List<Layer> layers2 = tester.layers;
     expect(layers1, isNot(equals(layers2)));
   });

packages/flutter/test/material/theme_test.dart

@@ -25,7 +25,7 @@ void main() {
                 key: popupMenuButtonKey,
                 itemBuilder: (BuildContext context) {
                   return <PopupMenuItem<String>>[
-                    new PopupMenuItem<String>(child: const Text('menuItem'))
+                    const PopupMenuItem<String>(child: const Text('menuItem'))
                   ];
                 }
               ),
@@ -71,7 +71,7 @@ void main() {
                   key: popupMenuButtonKey,
                   itemBuilder: (BuildContext context) {
                     return <PopupMenuItem<String>>[
-                      new PopupMenuItem<String>(child: const Text('menuItem'))
+                      const PopupMenuItem<String>(child: const Text('menuItem'))
                     ];
                   }
                 ),

packages/flutter/test/widgets/ticker_provider_test.dart

@@ -9,7 +9,7 @@ void main() {
   testWidgets('TickerMode', (WidgetTester tester) async {
     final Widget widget = new TickerMode(
       enabled: false,
-      child: new LinearProgressIndicator()
+      child: const LinearProgressIndicator()
     );
     expect(widget.toString, isNot(throwsException));
 
@@ -19,14 +19,14 @@ void main() {
 
     await tester.pumpWidget(new TickerMode(
       enabled: true,
-      child: new LinearProgressIndicator()
+      child: const LinearProgressIndicator()
     ));
 
     expect(tester.binding.transientCallbackCount, 1);
 
     await tester.pumpWidget(new TickerMode(
       enabled: false,
-      child: new LinearProgressIndicator()
+      child: const LinearProgressIndicator()
     ));
 
     expect(tester.binding.transientCallbackCount, 0);
@@ -34,7 +34,7 @@ void main() {
 
   testWidgets('Navigation with TickerMode', (WidgetTester tester) async {
     await tester.pumpWidget(new MaterialApp(
-      home: new LinearProgressIndicator(),
+      home: const LinearProgressIndicator(),
       routes: <String, WidgetBuilder>{
         '/test': (BuildContext context) => const Text('hello'),
       },