Fix error resolution when a completer is already set (#81014)

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

@@ -333,8 +333,6 @@ abstract class ImageProvider<T extends Object> {
       },
       (T? key, Object exception, StackTrace? stack) async {
         await null; // wait an event turn in case a listener has been added to the image stream.
-        final _ErrorImageCompleter imageCompleter = _ErrorImageCompleter();
-        stream.setCompleter(imageCompleter);
         InformationCollector? collector;
         assert(() {
           collector = () sync* {
@@ -344,7 +342,10 @@ abstract class ImageProvider<T extends Object> {
           };
           return true;
         }());
-        imageCompleter.setError(
+        if (stream.completer == null) {
+          stream.setCompleter(_ErrorImageCompleter());
+        }
+        stream.completer!.reportError(
           exception: exception,
           stack: stack,
           context: ErrorDescription('while resolving an image'),
@@ -1127,25 +1128,7 @@ class ExactAssetImage extends AssetBundleImageProvider {
 }
 
 // A completer used when resolving an image fails sync.
-class _ErrorImageCompleter extends ImageStreamCompleter {
-  _ErrorImageCompleter();
-
-  void setError({
-    DiagnosticsNode? context,
-    required Object exception,
-    StackTrace? stack,
-    InformationCollector? informationCollector,
-    bool silent = false,
-  }) {
-    reportError(
-      context: context,
-      exception: exception,
-      stack: stack,
-      informationCollector: informationCollector,
-      silent: silent,
-    );
-  }
-}
+class _ErrorImageCompleter extends ImageStreamCompleter {}
 
 /// The exception thrown when the HTTP request to load a network image fails.
 class NetworkImageLoadException implements Exception {

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

@@ -668,7 +668,6 @@ abstract class ImageStreamCompleter with Diagnosticable {
   /// messages, but errors during development will still be reported.
   ///
   /// See [FlutterErrorDetails] for further details on these values.
-  @protected
   @pragma('vm:notify-debugger-on-exception')
   void reportError({
     DiagnosticsNode? context,

packages/flutter/test/painting/image_provider_test.dart

@@ -90,7 +90,9 @@ void main() {
     await testZone.run(() async {
       final ImageProvider imageProvider = LoadErrorCompleterImageProvider();
       final Completer<bool> caughtError = Completer<bool>();
+      final Completer<bool> onErrorCompleter = Completer<bool>();
       FlutterError.onError = (FlutterErrorDetails details) {
+        onErrorCompleter.complete(true);
         throw Error();
       };
       final ImageStream result = imageProvider.resolve(ImageConfiguration.empty);
@@ -99,6 +101,7 @@ void main() {
         caughtError.complete(true);
       }));
       expect(await caughtError.future, true);
+      expect(await onErrorCompleter.future, true);
     });
     expect(uncaught, false);
   });