[framework] Remove danger zone (#100246)

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

@@ -435,38 +435,21 @@ abstract class ImageProvider<T extends Object> {
       didError = true;
     }
 
-    // If an error is added to a synchronous completer before a listener has been
-    // added, it can throw an error both into the zone and up the stack. Thus, it
-    // looks like the error has been caught, but it is in fact also bubbling to the
-    // zone. Since we cannot prevent all usage of Completer.sync here, or rather
-    // that changing them would be too breaking, we instead hook into the same
-    // zone mechanism to intercept the uncaught error and deliver it to the
-    // image stream's error handler. Note that these errors may be duplicated,
-    // hence the need for the `didError` flag.
-    final Zone dangerZone = Zone.current.fork(
-      specification: ZoneSpecification(
-        handleUncaughtError: (Zone zone, ZoneDelegate delegate, Zone parent, Object error, StackTrace stackTrace) {
-          handleError(error, stackTrace);
-        },
-      ),
-    );
-    dangerZone.runGuarded(() {
-      Future<T> key;
+    Future<T> key;
+    try {
+      key = obtainKey(configuration);
+    } catch (error, stackTrace) {
+      handleError(error, stackTrace);
+      return;
+    }
+    key.then<void>((T key) {
+      obtainedKey = key;
       try {
-        key = obtainKey(configuration);
+        successCallback(key, handleError);
       } catch (error, stackTrace) {
         handleError(error, stackTrace);
-        return;
       }
-      key.then<void>((T key) {
-        obtainedKey = key;
-        try {
-          successCallback(key, handleError);
-        } catch (error, stackTrace) {
-          handleError(error, stackTrace);
-        }
-      }).catchError(handleError);
-    });
+    }).catchError(handleError);
   }
 
   /// Called by [resolve] with the key returned by [obtainKey].

packages/flutter/test/painting/image_provider_test.dart

@@ -57,55 +57,6 @@ void main() {
     expect(await caughtError.future, true);
   });
 
-  test('resolve sync errors will be caught', () async {
-    bool uncaught = false;
-    final Zone testZone = Zone.current.fork(specification: ZoneSpecification(
-      handleUncaughtError: (Zone zone, ZoneDelegate zoneDelegate, Zone parent, Object error, StackTrace stackTrace) {
-        uncaught = true;
-      },
-    ));
-    await testZone.run(() async {
-      final ImageProvider imageProvider = LoadErrorImageProvider();
-      final Completer<bool> caughtError = Completer<bool>();
-      FlutterError.onError = (FlutterErrorDetails details) {
-        throw Error();
-      };
-      final ImageStream result = imageProvider.resolve(ImageConfiguration.empty);
-      result.addListener(ImageStreamListener((ImageInfo info, bool syncCall) {
-      }, onError: (dynamic error, StackTrace? stackTrace) {
-        caughtError.complete(true);
-      }));
-      expect(await caughtError.future, true);
-    });
-    expect(uncaught, false);
-  });
-
-  test('resolve errors in the completer will be caught', () async {
-    bool uncaught = false;
-    final Zone testZone = Zone.current.fork(specification: ZoneSpecification(
-      handleUncaughtError: (Zone zone, ZoneDelegate zoneDelegate, Zone parent, Object error, StackTrace stackTrace) {
-        uncaught = true;
-      },
-    ));
-    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);
-      result.addListener(ImageStreamListener((ImageInfo info, bool syncCall) {
-      }, onError: (dynamic error, StackTrace? stackTrace) {
-        caughtError.complete(true);
-      }));
-      expect(await caughtError.future, true);
-      expect(await onErrorCompleter.future, true);
-    });
-    expect(uncaught, false);
-  });
-
   test('File image with empty file throws expected error and evicts from cache', () async {
     final Completer<StateError> error = Completer<StateError>();
     FlutterError.onError = (FlutterErrorDetails details) {