fixed keyboardDismissBehavior on scroll without a drag (flutter#154675)

fixes flutter#154515, flutter#150048 and other similar issues where user non-draggable scrolls (mouse wheel, two-fingers) should behave same as draggable ones.

In this PR, scrollUpdateNotification.dragDetails check is removed and it has a supporting test which simulates a scroll which does not produce a drag.

Author: nick9822

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

@@ -276,7 +276,7 @@ class SingleChildScrollView extends StatelessWidget {
         child: scrollable,
         onNotification: (ScrollUpdateNotification notification) {
           final FocusScopeNode currentScope = FocusScope.of(context);
-          if (notification.dragDetails != null && !currentScope.hasPrimaryFocus && currentScope.hasFocus) {
+          if (!currentScope.hasPrimaryFocus && currentScope.hasFocus) {
             FocusManager.instance.primaryFocus?.unfocus();
           }
           return false;

packages/flutter/test/widgets/single_child_scroll_view_test.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:ui';
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -1118,4 +1120,47 @@ void main() {
 
     expect(tester.testTextInput.isVisible, isFalse);
   });
+
+  testWidgets('keyboardDismissBehavior on scroll without a drag test', (WidgetTester tester) async {
+    await tester.pumpWidget(MaterialApp(
+      home: Scaffold(
+        body: SizedBox(
+          height: 1000,
+          child: SingleChildScrollView(
+            keyboardDismissBehavior: ScrollViewKeyboardDismissBehavior.onDrag,
+            child: Column(
+              children: <Widget>[
+                Autocomplete<String>(
+                  optionsBuilder: (TextEditingValue textEditingValue) {
+                    return<String>['aardvark', 'bobcat', 'chameleon']
+                        .where((String option) {
+                      return option.contains(textEditingValue.text.toLowerCase());
+                    });
+                  },
+                ),
+                const SizedBox(height: 2000),
+              ],
+            ),
+          ),
+        ),
+      ),
+    ));
+
+    await tester.tap(find.byType(Autocomplete<String>));
+    await tester.pump();
+
+    await tester.enterText(find.byType(RawAutocomplete<String>),'aard');
+    await tester.pump();
+
+    expect(find.text('aardvark'), findsOneWidget);
+
+    final TestPointer testPointer = TestPointer(1, PointerDeviceKind.mouse);
+    final Offset scrollStart = tester.getCenter(find.byType(SingleChildScrollView));
+
+    testPointer.hover(scrollStart);
+    await tester.sendEventToBinding(testPointer.scroll(Offset(scrollStart.dx, scrollStart.dy - 100)));
+    await tester.pumpAndSettle();
+
+    expect(find.text('aardvark'), findsNothing);
+  });
 }