[web] Dispose a temporary image that may be created by instantiateImageCodecWithSize

Fixes flutter/flutter#147066

Author: jason-simmons

lib/web_ui/lib/src/engine/image_decoder.dart

@@ -229,15 +229,16 @@ class ResizingCodec implements ui.Codec {
   @override
   Future<ui.FrameInfo> getNextFrame() async {
     final ui.FrameInfo frameInfo = await delegate.getNextFrame();
-    return AnimatedImageFrameInfo(
-      frameInfo.duration,
-      scaleImage(
+    final ui.Image scaledImage = scaleImage(
         frameInfo.image,
         targetWidth: targetWidth,
         targetHeight: targetHeight,
         allowUpscaling: allowUpscaling,
-      ),
     );
+    if (!identical(frameInfo.image, scaledImage)) {
+      frameInfo.image.dispose();
+    }
+    return AnimatedImageFrameInfo(frameInfo.duration, scaledImage);
   }
 
   ui.Image scaleImage(

lib/web_ui/test/canvaskit/image_test.dart

@@ -21,6 +21,11 @@ void main() {
 void testMain() {
   setUpCanvasKitTest();
 
+  tearDown(() {
+    ui.Image.onCreate = null;
+    ui.Image.onDispose = null;
+  });
+
   test('toImage succeeds', () async {
     final ui.Image image = await _createImage();
     expect(image.runtimeType.toString(), equals('CkImage'));
@@ -44,8 +49,6 @@ void testMain() {
 
     expect(onCreateInvokedCount, 2);
     expect(createdImage, image2);
-
-    ui.Image.onCreate = null;
   });
 
   test('dispose() invokes onDispose once', () async {
@@ -65,8 +68,6 @@ void testMain() {
 
     expect(onDisposeInvokedCount, 2);
     expect(disposedImage, image2);
-
-    ui.Image.onDispose = null;
   });
 
   test('fetchImage fetches image in chunks', () async {
@@ -105,6 +106,30 @@ void testMain() {
     final BitmapSize? size = scaledImageSize(200, 100, 600, null);
     expect(size?.width, 600);
     expect(size?.height, 300);
+  }
+
+  test('instantiateImageCodecWithSize disposes temporary image', () async {
+    final Set<ui.Image> activeImages = <ui.Image>{};
+    ui.Image.onCreate = activeImages.add;
+    ui.Image.onDispose = activeImages.remove;
+
+    final ui.Image image = await _createImage();
+    final ByteData? imageData = await image.toByteData(format: ui.ImageByteFormat.png);
+    final ui.ImmutableBuffer imageBuffer = await ui.ImmutableBuffer.fromUint8List(imageData!.buffer.asUint8List());
+    image.dispose();
+
+    final ui.Codec codec = await ui.instantiateImageCodecWithSize(
+      imageBuffer,
+      getTargetSize: (w, h) => ui.TargetImageSize(width: w ~/ 2, height: h ~/ 2)
+    );
+    final ui.FrameInfo frameInfo = await codec.getNextFrame();
+
+    expect(activeImages.length, 1);
+
+    frameInfo.image.dispose();
+    codec.dispose();
+
+    expect(activeImages.length, 0);
   });
 }