Add checks for disposed images in FragmentShader.setImageSampler (#165214)

Author: jason-simmons

engine/src/flutter/lib/ui/painting.dart

@@ -5280,6 +5280,7 @@ base class FragmentShader extends Shader {
   /// results will be undefined.
   void setImageSampler(int index, Image image) {
     assert(!debugDisposed, 'Tried to access uniforms on a disposed Shader: $this');
+    assert(!image.debugDisposed, 'Image has been disposed');
     _setImageSampler(index, image._image);
   }
 

engine/src/flutter/lib/ui/painting/fragment_shader.cc

@@ -66,9 +66,15 @@ void ReusableFragmentShader::SetImageSampler(Dart_Handle index_handle,
       tonic::DartConverter<CanvasImage*>::FromDart(image_handle);
   if (index >= samplers_.size()) {
     Dart_ThrowException(tonic::ToDart("Sampler index out of bounds"));
+    return;
+  }
+  if (!image || !image->image()) {
+    Dart_ThrowException(tonic::ToDart("Image has been disposed"));
+    return;
   }
   if (!image->image()->isUIThreadSafe()) {
     Dart_ThrowException(tonic::ToDart("Image is not thread-safe"));
+    return;
   }
 
   // TODO(115794): Once the DlImageSampling enum is replaced, expose the

engine/src/flutter/testing/dart/fragment_shader_test.dart

@@ -91,6 +91,30 @@ void main() async {
     },
   );
 
+  test('FragmentShader setImageSampler asserts if image is disposed', () async {
+    final FragmentProgram program = await FragmentProgram.fromAsset('blue_green_sampler.frag.iplr');
+    final Image blueGreenImage = await _createBlueGreenImage();
+    final FragmentShader fragmentShader = program.fragmentShader();
+
+    try {
+      blueGreenImage.dispose();
+      expect(
+        () {
+          fragmentShader.setImageSampler(0, blueGreenImage);
+        },
+        throwsA(
+          isA<AssertionError>().having(
+            (AssertionError e) => e.message,
+            'message',
+            contains('Image has been disposed'),
+          ),
+        ),
+      );
+    } finally {
+      fragmentShader.dispose();
+    }
+  });
+
   test('Disposed FragmentShader on Paint', () async {
     final FragmentProgram program = await FragmentProgram.fromAsset('blue_green_sampler.frag.iplr');
     final Image blueGreenImage = await _createBlueGreenImage();