Revert "Add Form.onSaved (#30643)" (#30793)

This reverts commit 949023b2.

packages/flutter/lib/src/widgets/form.dart

@@ -72,7 +72,6 @@ class Form extends StatefulWidget {
     this.autovalidate = false,
     this.onWillPop,
     this.onChanged,
-    this.onSaved,
   }) : assert(child != null),
        super(key: key);
 
@@ -119,13 +118,6 @@ class Form extends StatefulWidget {
   /// will rebuild.
   final VoidCallback onChanged;
 
-  /// Called when the form is saved (after all the form fields have been saved).
-  ///
-  /// See also:
-  ///
-  ///  * [FormState.save]
-  final VoidCallback onSaved;
-
   @override
   FormState createState() => FormState();
 }
@@ -180,8 +172,6 @@ class FormState extends State<Form> {
   void save() {
     for (FormFieldState<dynamic> field in _fields)
       field.save();
-    if (widget.onSaved != null)
-      widget.onSaved();
   }
 
   /// Resets every [FormField] that is a descendant of this [Form] back to its

packages/flutter/test/widgets/form_test.dart

@@ -6,10 +6,9 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 
 void main() {
-  testWidgets('onSaved callbacks are called', (WidgetTester tester) async {
+  testWidgets('onSaved callback is called', (WidgetTester tester) async {
     final GlobalKey<FormState> formKey = GlobalKey<FormState>();
     String fieldValue;
-    bool fieldModifiedSinceFormOnSaved;
 
     Widget builder() {
       return MediaQuery(
@@ -20,12 +19,8 @@ void main() {
             child: Material(
               child: Form(
                 key: formKey,
-                onSaved: () { fieldModifiedSinceFormOnSaved = false; },
                 child: TextFormField(
-                  onSaved: (String value) {
-                    fieldValue = value;
-                    fieldModifiedSinceFormOnSaved = true;
-                  },
+                  onSaved: (String value) { fieldValue = value; },
                 ),
               ),
             ),
@@ -43,7 +38,6 @@ void main() {
       formKey.currentState.save();
       // pump'ing is unnecessary because callback happens regardless of frames
       expect(fieldValue, equals(testValue));
-      expect(fieldModifiedSinceFormOnSaved, isFalse);
     }
 
     await checkText('Test');