[null-safety] update to several framework test cases/APIs for null assertions (#62946)

packages/flutter/lib/src/foundation/diagnostics.dart

@@ -2053,7 +2053,7 @@ class PercentProperty extends DoubleProperty {
   /// The [showName] and [level] arguments must not be null.
   PercentProperty(
     String name,
-    double fraction, {
+    double? fraction, {
     String? ifNull,
     bool showName = true,
     String? tooltip,

packages/flutter/lib/src/painting/image_cache.dart

@@ -2,7 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-
 import 'dart:developer';
 import 'dart:ui' show hashValues;
 

packages/flutter/lib/src/services/binary_messenger.dart

@@ -49,7 +49,7 @@ abstract class BinaryMessenger {
   ///
   /// This method is useful for tests or test harnesses that want to assert the
   /// handler for the specified channel has not been altered by a previous test.
-  bool checkMessageHandler(String channel, MessageHandler handler);
+  bool checkMessageHandler(String channel, MessageHandler? handler);
 
   /// Set a mock callback for intercepting messages from the [send] method on
   /// this class, on the given channel, without decoding them.
@@ -70,7 +70,7 @@ abstract class BinaryMessenger {
   /// This method is useful for tests or test harnesses that want to assert the
   /// mock handler for the specified channel has not been altered by a previous
   /// test.
-  bool checkMockMessageHandler(String channel, MessageHandler handler);
+  bool checkMockMessageHandler(String channel, MessageHandler? handler);
 }
 
 /// The default instance of [BinaryMessenger].

packages/flutter/lib/src/services/binding.dart

@@ -216,8 +216,8 @@ mixin ServicesBinding on BindingBase, SchedulerBinding {
   /// To use a different [RestorationManager] subclasses can override
   /// [createRestorationManager], which is called to create the instance
   /// returned by this getter.
-  RestorationManager get restorationManager => _restorationManager;
-  late RestorationManager _restorationManager;
+  RestorationManager get restorationManager => _restorationManager!;
+  RestorationManager? _restorationManager;
 
   /// Creates the [RestorationManager] instance available via
   /// [restorationManager].
@@ -319,7 +319,7 @@ class _DefaultBinaryMessenger extends BinaryMessenger {
   }
 
   @override
-  bool checkMessageHandler(String channel, MessageHandler handler) => _handlers[channel] == handler;
+  bool checkMessageHandler(String channel, MessageHandler? handler) => _handlers[channel] == handler;
 
   @override
   void setMockMessageHandler(String channel, MessageHandler? handler) {
@@ -330,5 +330,5 @@ class _DefaultBinaryMessenger extends BinaryMessenger {
   }
 
   @override
-  bool checkMockMessageHandler(String channel, MessageHandler handler) => _mockHandlers[channel] == handler;
+  bool checkMockMessageHandler(String channel, MessageHandler? handler) => _mockHandlers[channel] == handler;
 }

packages/flutter/lib/src/services/platform_channel.dart

@@ -2,7 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-
 import 'dart:async';
 import 'dart:typed_data';
 

packages/flutter/test/foundation/change_notifier_test.dart

@@ -210,8 +210,8 @@ void main() {
   test('Cannot use a disposed ChangeNotifier', () {
     final TestNotifier source = TestNotifier();
     source.dispose();
-    expect(() { source.addListener(null); }, throwsFlutterError);
-    expect(() { source.removeListener(null); }, throwsFlutterError);
+    expect(() { source.addListener(() { }); }, throwsFlutterError);
+    expect(() { source.removeListener(() { }); }, throwsFlutterError);
     expect(() { source.dispose(); }, throwsFlutterError);
     expect(() { source.notify(); }, throwsFlutterError);
   });

packages/flutter/test/painting/image_provider_test.dart

@@ -136,7 +136,9 @@ void main() {
     final File file = fs.file('/empty.png')..createSync(recursive: true);
     final FileImage provider = FileImage(file);
 
-    expect(provider.load(provider, null), isA<MultiFrameImageStreamCompleter>());
+    expect(provider.load(provider, (Uint8List bytes, {int cacheWidth, int cacheHeight, bool allowUpscaling}) async {
+      return Future<Codec>.value(FakeCodec());
+    }), isA<MultiFrameImageStreamCompleter>());
 
     expect(await error.future, isStateError);
   });

packages/flutter/test/scheduler/ticker_test.dart

@@ -96,7 +96,7 @@ void main() {
     Ticker ticker;
 
     void testFunction() {
-      ticker = Ticker(null);
+      ticker = Ticker((Duration _) { });
     }
 
     testFunction();

packages/flutter/test/widgets/binding_test.dart

@@ -194,7 +194,7 @@ void main() {
   testWidgets('scheduleFrameCallback error control test', (WidgetTester tester) async {
     FlutterError error;
     try {
-      tester.binding.scheduleFrameCallback(null, rescheduling: true);
+      tester.binding.scheduleFrameCallback((Duration _) { }, rescheduling: true);
     } on FlutterError catch (e) {
       error = e;
     }

packages/flutter/test/widgets/image_test.dart

@@ -797,12 +797,12 @@ void main() {
     expect(listeners.length, 2);
 
     // Make sure the first listener can be called re-entrantly
-    listeners[1].onImage(null, null);
-    listeners[1].onImage(null, null);
+    listeners[1].onImage(null, false);
+    listeners[1].onImage(null, false);
 
     // Make sure the second listener can be called re-entrantly.
-    listeners[0].onImage(null, null);
-    listeners[0].onImage(null, null);
+    listeners[0].onImage(null, false);
+    listeners[0].onImage(null, false);
   });
 
   testWidgets('Precache completes with onError on error', (WidgetTester tester) async {

packages/flutter_test/lib/src/window.dart

@@ -190,7 +190,7 @@ class TestWindow implements Window {
 
   @override
   String get initialLifecycleState => _initialLifecycleStateTestValue;
-  String _initialLifecycleStateTestValue;
+  String _initialLifecycleStateTestValue = '';
   /// Sets a faked initialLifecycleState for testing.
   set initialLifecycleStateTestValue(String state) {
     _initialLifecycleStateTestValue = state;