shader warm up with canvaskit and corresponding test (#113060)

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

@@ -69,3 +69,6 @@ const double precisionErrorTolerance = 1e-10;
 
 /// A constant that is true if the application was compiled to run on the web.
 const bool kIsWeb = bool.fromEnvironment('dart.library.js_util');
+
+/// A constant that is true if the application is using canvasKit
+const bool isCanvasKit = bool.fromEnvironment('FLUTTER_WEB_USE_SKIA');

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

@@ -87,7 +87,7 @@ abstract class ShaderWarmUp {
     await warmUpOnCanvas(canvas);
     final ui.Picture picture = recorder.endRecording();
     assert(debugCaptureShaderWarmUpPicture(picture));
-    if (!kIsWeb) { // Picture.toImage is not yet implemented on the web.
+    if (!kIsWeb || isCanvasKit) { // Picture.toImage is not yet implemented on the web.
       final TimelineTask shaderWarmUpTask = TimelineTask();
       shaderWarmUpTask.start('Warm-up shader');
       try {

packages/flutter/test/painting/shader_warm_up_test.dart

+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:ui' as ui;
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/widgets.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+Future<void> main() async {
+  test('ShaderWarmUp', () {
+    final FakeShaderWarmUp shaderWarmUp = FakeShaderWarmUp();
+    PaintingBinding.shaderWarmUp = shaderWarmUp;
+    debugCaptureShaderWarmUpImage = expectAsync1((ui.Image image) => true);
+    WidgetsFlutterBinding.ensureInitialized();
+    expect(shaderWarmUp.ranWarmUp, true);
+  }, skip: kIsWeb && !isCanvasKit); // [intended] Testing only for canvasKit
+}
+
+class FakeShaderWarmUp extends ShaderWarmUp {
+  bool ranWarmUp = false;
+
+  @override
+  Future<bool> warmUpOnCanvas(ui.Canvas canvas) {
+    ranWarmUp = true;
+    return Future<bool>.delayed(Duration.zero, () => true);
+  }
+}