Renamed DropDown to Dropdown. (#5897)

Fixes #3208.

examples/flutter_gallery/lib/demo/buttons_demo.dart

@@ -143,7 +143,7 @@ class _ButtonsDemoState extends State<ButtonsDemo> {
         children: <Widget>[
           new ListItem(
             title: new Text('Scrollable dropdown:'),
-            trailing: new DropDownButton<String>(
+            trailing: new DropdownButton<String>(
               value: dropdown1Value,
               onChanged: (String newValue) {
                 setState(() {
@@ -156,7 +156,7 @@ class _ButtonsDemoState extends State<ButtonsDemo> {
                   'Bit', 'More', 'Five', 'Six', 'Seven', 'Eight', 'Nine', 'Ten'
                  ]
                 .map((String value) {
-                  return new DropDownMenuItem<String>(
+                  return new DropdownMenuItem<String>(
                     value: value,
                     child: new Text(value));
                 })
@@ -168,7 +168,7 @@ class _ButtonsDemoState extends State<ButtonsDemo> {
           ),
           new ListItem(
             title: new Text('Simple dropdown:'),
-            trailing: new DropDownButton<String>(
+            trailing: new DropdownButton<String>(
               value: dropdown2Value,
               onChanged: (String newValue) {
                 setState(() {
@@ -178,7 +178,7 @@ class _ButtonsDemoState extends State<ButtonsDemo> {
               },
               items: <String>['One', 'Two', 'Free', 'Four']
                 .map((String value) {
-                  return new DropDownMenuItem<String>(
+                  return new DropdownMenuItem<String>(
                     value: value,
                     child: new Text(value));
                 })

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

@@ -73,16 +73,16 @@ class OrderItem extends StatelessWidget {
                   new SizedBox(height: 16.0),
                   new Padding(
                     padding: const EdgeInsets.only(top: 8.0, bottom: 8.0, right: 88.0),
-                    child: new DropDownButtonHideUnderline(
+                    child: new DropdownButtonHideUnderline(
                       child: new Container(
                         decoration: new BoxDecoration(
                           border: new Border.all(
                             color: const Color(0xFFD9D9D9)
                           )
                         ),
-                        child: new DropDownButton<int>(
+                        child: new DropdownButton<int>(
                           items: <int>[0, 1, 2, 3, 4, 5].map((int value) {
-                            return new DropDownMenuItem<int>(
+                            return new DropdownMenuItem<int>(
                               value: value,
                               child: new Padding(
                                 padding: const EdgeInsets.only(left: 8.0),

examples/flutter_gallery/lib/gallery/example_code.dart

@@ -56,7 +56,7 @@ new FlatButton(
 String dropdownValue;
 
 // Drop down button with string values.
-new DropDownButton<String>(
+new DropdownButton<String>(
   value: dropdownValue,
   onChanged: (String newValue) {
     // null indicates the user didn't select a
@@ -68,7 +68,7 @@ new DropDownButton<String>(
   },
   items: <String>['One', 'Two', 'Free', 'Four']
     .map((String value) {
-      return new DropDownMenuItem<String>(
+      return new DropdownMenuItem<String>(
         value: value,
         child: new Text(value));
     })

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

@@ -153,7 +153,7 @@ class DataCell {
   /// Creates an object to hold the data for a cell in a [DataTable].
   ///
   /// The first argument is the widget to show for the cell, typically
-  /// a [Text] or [DropDownButton] widget; this becomes the [widget]
+  /// a [Text] or [DropdownButton] widget; this becomes the [widget]
   /// property and must not be null.
   ///
   /// If the cell has no data, then a [Text] widget with placeholder
@@ -170,7 +170,7 @@ class DataCell {
 
   /// The data for the row.
   ///
-  /// Typically a [Text] widget or a [DropDownButton] widget.
+  /// Typically a [Text] widget or a [DropdownButton] widget.
   ///
   /// If the cell has no data, then a [Text] widget with placeholder
   /// text should be provided instead, and [placeholder] should be set
@@ -470,7 +470,7 @@ class DataTable extends StatelessWidget {
           data: new IconThemeData(
             color: isLightTheme ? Colors.black54 : Colors.white70
           ),
-          child: new DropDownButtonHideUnderline(child: label)
+          child: new DropdownButtonHideUnderline(child: label)
         )
       )
     );

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

@@ -32,7 +32,7 @@ import 'theme.dart';
 /// See also:
 ///
 ///  * [RaisedButton]
-///  * [DropDownButton]
+///  * [DropdownButton]
 ///  * <https://www.google.com/design/spec/components/buttons.html>
 class FlatButton extends StatelessWidget {
   /// Creates a flat button.

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

@@ -307,8 +307,8 @@ class PaginatedDataTableState extends State<PaginatedDataTable> {
     if (config.onRowsPerPageChanged != null) {
       List<Widget> availableRowsPerPage = config.availableRowsPerPage
         .where((int value) => value <= _rowCount)
-        .map/*<DropDownMenuItem<int>>*/((int value) {
-          return new DropDownMenuItem<int>(
+        .map/*<DropdownMenuItem<int>>*/((int value) {
+          return new DropdownMenuItem<int>(
             value: value,
             child: new Text('$value')
           );
@@ -316,8 +316,8 @@ class PaginatedDataTableState extends State<PaginatedDataTable> {
         .toList();
       footerWidgets.addAll(<Widget>[
         new Text('Rows per page:'),
-        new DropDownButtonHideUnderline(
-          child: new DropDownButton<int>(
+        new DropdownButtonHideUnderline(
+          child: new DropdownButton<int>(
             items: availableRowsPerPage,
             value: config.rowsPerPage,
             onChanged: config.onRowsPerPageChanged,

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

@@ -29,7 +29,7 @@ import 'theme.dart';
 /// See also:
 ///
 ///  * [FlatButton]
-///  * [DropDownButton]
+///  * [DropdownButton]
 ///  * [FloatingActionButton]
 ///  * <https://www.google.com/design/spec/components/buttons.html>
 class RaisedButton extends StatelessWidget {

packages/flutter/test/material/drop_down_test.dart

@@ -8,15 +8,15 @@ import 'package:flutter/material.dart';
 void main() {
   testWidgets('Drop down screen edges', (WidgetTester tester) async {
     int value = 4;
-    List<DropDownMenuItem<int>> items = <DropDownMenuItem<int>>[];
+    List<DropdownMenuItem<int>> items = <DropdownMenuItem<int>>[];
     for (int i = 0; i < 20; ++i)
-      items.add(new DropDownMenuItem<int>(value: i, child: new Text('$i')));
+      items.add(new DropdownMenuItem<int>(value: i, child: new Text('$i')));
 
     void handleChanged(int newValue) {
       value = newValue;
     }
 
-    DropDownButton<int> button = new DropDownButton<int>(
+    DropdownButton<int> button = new DropdownButton<int>(
       value: value,
       onChanged: handleChanged,
       items: items