title: Flutter - 'enableInteractiveSelection' not working for EditableText
body: <p>I am trying to use Flutter's 'EditableText' class.
  I have 3 questions regarding it.</p>
  
  <ol>
  <li><p>'enableInteractiveSelection' is set to be 'true' but I do not see 'cut, copy, paste'.</p></li>
  <li><p>'onSelectionChanged' seems not working. I don't see anything in the console even when I change selection.</p></li>
  <li><p>can someone explain me how to use 'selectionControls'?</p></li>
  </ol>
  
  <p>Below is my 'EditableText' code</p>
  
  <pre><code>import 'package:flutter/material.dart';
  
  void main() =&gt; runApp(MyApp());
  
  class MyApp extends StatelessWidget {
    @override
    Widget build(BuildContext context) {
      return MaterialApp(
        title: 'Flutter Demo',
        theme: ThemeData(
          primarySwatch: Colors.blue,
        ),
        home: MyHomePage(title: 'Editable Text'),
      );
    }
  }
  
  class MyHomePage extends StatefulWidget {
    MyHomePage({Key key, this.title}) : super(key: key);
    final String title;
  
    @override
    _MyHomePageState createState() =&gt; _MyHomePageState();
  }
  
  class _MyHomePageState extends State&lt;MyHomePage&gt; {
    TextEditingController _mainContentController;
    TextSelectionControls _mainContentSelectionController;
    FocusNode _textFieldFocusNode;
  
    @override
    void initState() {
      _textFieldFocusNode = FocusNode();
      _mainContentController = TextEditingController();
      super.initState();
    }
  
    @override
    void dispose() {
      _mainContentController.dispose();
      _textFieldFocusNode.dispose();
      super.dispose();
    }
  
    @override
    Widget build(BuildContext context) {
      return Scaffold(
        appBar: AppBar(
          title: Text(widget.title),
        ),
        body: Column(
          children: &lt;Widget&gt;[
            Text('Editable Text Below'),
            Container(
              padding: EdgeInsets.all(10),
              child: EditableText(
                focusNode: _textFieldFocusNode,
                controller: _mainContentController,
                selectionColor: Colors.blue,
                style: TextStyle(color: Colors.black, fontSize: 17),
                cursorColor: Colors.blue,
                textInputAction: TextInputAction.newline,
                maxLines: null,
                onChanged: (text) {
                  print(text);
                },
                enableInteractiveSelection: true,
                onSelectionChanged:
                    (TextSelection textSelection, SelectionChangedCause cause) {
                  print('working?');
                  print(textSelection.start);
                  print(cause);
                },
                selectionControls: _mainContentSelectionController,
              ),
            )
          ],
        ),
      );
    }
  }
  </code></pre>