Selection controls internationalization (#22443)

* Fix internationalization issues with cupertinoTextSelectionControls

packages/flutter/lib/src/cupertino/localizations.dart

@@ -185,6 +185,19 @@ abstract class CupertinoLocalizations {
   /// ```dart
   /// CupertinoLocalizations.of(context).anteMeridiemAbbreviation;
   /// ```
+
+  /// The term used for cutting
+  String get cutButtonLabel;
+
+  /// The term used for copying
+  String get copyButtonLabel;
+
+  /// The term used for pasting
+  String get pasteButtonLabel;
+
+  /// The term used for selecting everything
+  String get selectAllButtonLabel;
+
   static CupertinoLocalizations of(BuildContext context) {
     return Localizations.of<CupertinoLocalizations>(context, CupertinoLocalizations);
   }
@@ -252,6 +265,8 @@ class DefaultCupertinoLocalizations implements CupertinoLocalizations {
     'December',
   ];
 
+
+
   @override
   String datePickerYear(int yearIndex) => yearIndex.toString();
 
@@ -317,6 +332,18 @@ class DefaultCupertinoLocalizations implements CupertinoLocalizations {
   @override
   String timerPickerSecondLabel(int second) => 'sec';
 
+  @override
+  String get cutButtonLabel => 'Cut';
+
+  @override
+  String get copyButtonLabel => 'Copy';
+
+  @override
+  String get pasteButtonLabel => 'Paste';
+
+  @override
+  String get selectAllButtonLabel => 'Select All';
+
   /// Creates an object that provides US English resource values for the
   /// cupertino library widgets.
   ///

packages/flutter/lib/src/cupertino/text_selection.dart

@@ -8,6 +8,7 @@ import 'package:flutter/widgets.dart';
 import 'package:flutter/rendering.dart';
 
 import 'button.dart';
+import 'localizations.dart';
 
 // Padding around the line at the edge of the text selection that has 0 width and
 // the height of the text font.
@@ -74,26 +75,27 @@ class _TextSelectionToolbar extends StatelessWidget {
     final List<Widget> items = <Widget>[];
     final Widget onePhysicalPixelVerticalDivider =
     SizedBox(width: 1.0 / MediaQuery.of(context).devicePixelRatio);
+    final CupertinoLocalizations localizations = CupertinoLocalizations.of(context);
 
     if (handleCut != null)
-      items.add(_buildToolbarButton('Cut', handleCut));
+      items.add(_buildToolbarButton(localizations.cutButtonLabel, handleCut));
 
     if (handleCopy != null) {
       if (items.isNotEmpty)
         items.add(onePhysicalPixelVerticalDivider);
-      items.add(_buildToolbarButton('Copy', handleCopy));
+      items.add(_buildToolbarButton(localizations.copyButtonLabel, handleCopy));
     }
 
     if (handlePaste != null) {
       if (items.isNotEmpty)
         items.add(onePhysicalPixelVerticalDivider);
-      items.add(_buildToolbarButton('Paste', handlePaste));
+      items.add(_buildToolbarButton(localizations.pasteButtonLabel, handlePaste));
     }
 
     if (handleSelectAll != null) {
       if (items.isNotEmpty)
         items.add(onePhysicalPixelVerticalDivider);
-      items.add(_buildToolbarButton('Select All', handleSelectAll));
+      items.add(_buildToolbarButton(localizations.selectAllButtonLabel, handleSelectAll));
     }
 
     final Widget triangle = SizedBox.fromSize(