prepare for lint update of prefer_final_fields (#35059)

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

@@ -2707,7 +2707,7 @@ class DiagnosticsProperty<T> extends DiagnosticsNode {
   /// [defaultValue] has type [T] or is [kNoDefaultValue].
   final Object defaultValue;
 
-  DiagnosticLevel _defaultLevel;
+  final DiagnosticLevel _defaultLevel;
 
   /// Priority level of the diagnostic used to control which diagnostics should
   /// be shown and filtered.

packages/flutter/lib/src/material/material.dart

@@ -561,7 +561,7 @@ abstract class InkFeature {
   /// Typically used by subclasses to call
   /// [MaterialInkController.markNeedsPaint] when they need to repaint.
   MaterialInkController get controller => _controller;
-  _RenderInkFeatures _controller;
+  final _RenderInkFeatures _controller;
 
   /// The render box whose visual position defines the frame of reference for this ink feature.
   final RenderBox referenceBox;

packages/flutter/lib/src/material/range_slider.dart

@@ -721,7 +721,7 @@ class _RenderRangeSlider extends RenderBox {
 
   static const Duration _minimumInteractionTime = Duration(milliseconds: 500);
 
-  _RangeSliderState _state;
+  final _RangeSliderState _state;
   Animation<double> _overlayAnimation;
   Animation<double> _valueIndicatorAnimation;
   Animation<double> _enableAnimation;

packages/flutter/lib/src/material/slider.dart

@@ -706,7 +706,7 @@ class _RenderSlider extends RenderBox {
   ];
   double get _minPreferredTrackHeight => _sliderTheme.trackHeight;
 
-  _SliderState _state;
+  final _SliderState _state;
   Animation<double> _overlayAnimation;
   Animation<double> _valueIndicatorAnimation;
   Animation<double> _enableAnimation;

packages/flutter/lib/src/rendering/view.dart

@@ -84,7 +84,7 @@ class RenderView extends RenderObject with RenderObjectWithChildMixin<RenderBox>
     markNeedsLayout();
   }
 
-  ui.Window _window;
+  final ui.Window _window;
 
   /// Whether Flutter should automatically compute the desired system UI.
   ///

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

@@ -505,9 +505,9 @@ class AndroidViewController {
 
   _AndroidViewState _state;
 
-  dynamic _creationParams;
+  final dynamic _creationParams;
 
-  MessageCodec<dynamic> _creationParamsCodec;
+  final MessageCodec<dynamic> _creationParamsCodec;
 
   final List<PlatformViewCreatedCallback> _platformViewCreatedCallbacks = <PlatformViewCreatedCallback>[];
 

packages/flutter/test/painting/image_resolution_test.dart

@@ -14,7 +14,7 @@ import 'package:flutter_test/flutter_test.dart';
 class TestAssetBundle extends CachingAssetBundle {
   TestAssetBundle(this._assetBundleMap);
 
-  Map<String, List<String>> _assetBundleMap;
+  final Map<String, List<String>> _assetBundleMap;
 
   Map<String, int> loadCallCount = <String, int>{};
 

packages/flutter_test/lib/src/widget_tester.dart

@@ -769,7 +769,7 @@ typedef _TickerDisposeCallback = void Function(_TestTicker ticker);
 class _TestTicker extends Ticker {
   _TestTicker(TickerCallback onTick, this._onDispose) : super(onTick);
 
-  _TickerDisposeCallback _onDispose;
+  final _TickerDisposeCallback _onDispose;
 
   @override
   void dispose() {

packages/flutter_tools/lib/src/android/android_emulator.dart

@@ -30,7 +30,7 @@ class AndroidEmulator extends Emulator {
   AndroidEmulator(String id, [this._properties])
     : super(id, _properties != null && _properties.isNotEmpty);
 
-  Map<String, String> _properties;
+  final Map<String, String> _properties;
 
   // Android Studio uses the ID with underscores replaced with spaces
   // for the name if displayname is not set so we do the same.

packages/flutter_tools/lib/src/artifacts.dart

@@ -260,7 +260,7 @@ class LocalEngineArtifacts extends Artifacts {
 
   final String _engineSrcPath;
   final String engineOutPath; // TODO(goderbauer): This should be private.
-  String _hostEngineOutPath;
+  final String _hostEngineOutPath;
 
   @override
   String getArtifactPath(Artifact artifact, { TargetPlatform platform, BuildMode mode }) {

packages/flutter_tools/lib/src/compile.dart

@@ -450,8 +450,8 @@ class ResidentCompiler {
   String _sdkRoot;
   Process _server;
   final StdoutHandler _stdoutHandler;
-  String _initializeFromDill;
-  bool _unsafePackageSerialization;
+  final String _initializeFromDill;
+  final bool _unsafePackageSerialization;
   final List<String> _experimentalFlags;
   bool _compileRequestNeedsConfirmation = false;
 

packages/flutter_tools/lib/src/devfs.dart

@@ -369,7 +369,7 @@ class DevFS {
   final _DevFSHttpWriter _httpWriter;
   final String fsName;
   final Directory rootDirectory;
-  String _packagesFilePath;
+  final String _packagesFilePath;
   final Set<String> assetPathsToEvict = <String>{};
   List<Uri> sources = <Uri>[];
   DateTime lastCompiled;

packages/flutter_tools/lib/src/fuchsia/fuchsia_device.dart

@@ -59,8 +59,8 @@ class _FuchsiaLogReader extends DeviceLogReader {
   // \S matches non-whitespace characters.
   static final RegExp _flutterLogOutput = RegExp(r'INFO: \S+\(flutter\): ');
 
-  FuchsiaDevice _device;
-  ApplicationPackage _app;
+  final FuchsiaDevice _device;
+  final ApplicationPackage _app;
 
   @override
   String get name => _device.name;

packages/flutter_tools/test/runner/flutter_command_test.dart

@@ -355,7 +355,7 @@ class MockDevice extends Mock implements Device {
   @override
   final bool ephemeral;
 
-  bool _isSupported;
+  final bool _isSupported;
 
   @override
   bool isSupportedForProject(FlutterProject flutterProject) => _isSupported;