diff --git a/sdk/lib/html/dart2js/html_dart2js.dart b/sdk/lib/html/dart2js/html_dart2js.dart
index 1bb284fe162..77a36ed1898 100644
--- a/sdk/lib/html/dart2js/html_dart2js.dart
+++ b/sdk/lib/html/dart2js/html_dart2js.dart
@@ -744,6 +744,7 @@ class AnimationEffectTiming extends AnimationEffectTimingReadOnly {
 
   // Shadowing definition.
 
+  @Returns('num|String|Null')
   Object get duration native;
 
   set duration(Object value) native;
diff --git a/sdk/lib/svg/dart2js/svg_dart2js.dart b/sdk/lib/svg/dart2js/svg_dart2js.dart
index 5704564d778..c54ac08c685 100644
--- a/sdk/lib/svg/dart2js/svg_dart2js.dart
+++ b/sdk/lib/svg/dart2js/svg_dart2js.dart
@@ -3244,7 +3244,7 @@ class SvgElement extends Element implements GlobalEventHandlers, NoncedElement {
   SvgElement.created() : super.created();
 
   // Shadowing definition.
-
+  @JSName('className')
   AnimatedString get _svgClassName native;
 
   @JSName('ownerSVGElement')
diff --git a/sdk_nnbd/lib/html/dart2js/html_dart2js.dart b/sdk_nnbd/lib/html/dart2js/html_dart2js.dart
index 94b857b4936..04dcc3d96ea 100644
--- a/sdk_nnbd/lib/html/dart2js/html_dart2js.dart
+++ b/sdk_nnbd/lib/html/dart2js/html_dart2js.dart
@@ -745,6 +745,7 @@ class AnimationEffectTiming extends AnimationEffectTimingReadOnly {
 
   // Shadowing definition.
 
+  @Returns('num|String|Null')
   Object? get duration native;
 
   set duration(Object? value) native;
diff --git a/sdk_nnbd/lib/svg/dart2js/svg_dart2js.dart b/sdk_nnbd/lib/svg/dart2js/svg_dart2js.dart
index eea4d4995fc..ebb90155e14 100644
--- a/sdk_nnbd/lib/svg/dart2js/svg_dart2js.dart
+++ b/sdk_nnbd/lib/svg/dart2js/svg_dart2js.dart
@@ -3282,7 +3282,7 @@ class SvgElement extends Element implements GlobalEventHandlers, NoncedElement {
   SvgElement.created() : super.created();
 
   // Shadowing definition.
-
+  @JSName('className')
   AnimatedString get _svgClassName native;
 
   @JSName('ownerSVGElement')
diff --git a/tools/dom/scripts/dartmetadata.py b/tools/dom/scripts/dartmetadata.py
index f7a6bcb393e..71f76022222 100644
--- a/tools/dom/scripts/dartmetadata.py
+++ b/tools/dom/scripts/dartmetadata.py
@@ -30,8 +30,7 @@ _dart2js_annotations = monitored.Dict(
     'dartmetadata._dart2js_annotations',
     {
         'AnimationEffectTiming.duration': [
-            "@Creates('Null')",
-            "@Returns('num|String')",
+            "@Returns('num|String|Null')",
         ],
         'ArrayBufferView': [
             "@Creates('TypedData')",
diff --git a/tools/dom/scripts/systemhtml.py b/tools/dom/scripts/systemhtml.py
index 4807cf8f583..70248c60f46 100644
--- a/tools/dom/scripts/systemhtml.py
+++ b/tools/dom/scripts/systemhtml.py
@@ -1394,6 +1394,14 @@ class Dart2JSBackend(HtmlDartGenerator):
             self._AddAttributeUsingProperties(attribute, html_name, read_only)
             return
 
+        output_type = self.SecureOutputType(attribute.type.id,
+                                            can_narrow_type=read_only,
+                                            nullable=attribute.type.nullable)
+
+        rename = self._RenamingAnnotation(attribute.id, html_name)
+        metadata = self._Metadata(attribute.type.id, attribute.id, output_type,
+            attribute.type.nullable)
+
         # If the attribute is shadowing, we can't generate a shadowing
         # getter or setter (Issue 1633).
         # TODO(sra): _FindShadowedAttribute does not take into account the html
@@ -1426,7 +1434,8 @@ class Dart2JSBackend(HtmlDartGenerator):
                                 'TreatNullAs' in attribute.ext_attrs))
                     return
             self._members_emitter.Emit('\n  // Shadowing definition.')
-            self._AddAttributeUsingProperties(attribute, html_name, read_only)
+            self._AddAttributeUsingProperties(attribute, html_name, read_only,
+                rename, metadata)
             return
 
         # If the attribute is shadowed incompatibly in a subclass then we also
@@ -1438,23 +1447,18 @@ class Dart2JSBackend(HtmlDartGenerator):
         if (self._interface.id == 'DOMMatrixReadOnly' or
                 self._interface.id == 'DOMPointReadOnly' or
                 self._interface.id == 'DOMRectReadOnly'):
-            self._AddAttributeUsingProperties(attribute, html_name, read_only)
+            self._AddAttributeUsingProperties(attribute, html_name, read_only,
+                rename, metadata)
             return
 
         # If the type has a conversion we need a getter or setter to contain the
         # conversion code.
         if (self._OutputConversion(attribute.type.id, attribute.id) or
                 self._InputConversion(attribute.type.id, attribute.id)):
-            self._AddAttributeUsingProperties(attribute, html_name, read_only)
+            self._AddAttributeUsingProperties(attribute, html_name, read_only,
+                rename, metadata)
             return
 
-        rename = self._RenamingAnnotation(attribute.id, html_name)
-        output_type = self.SecureOutputType(attribute.type.id,
-                                            can_narrow_type=read_only,
-                                            nullable=attribute.type.nullable)
-        metadata = self._Metadata(attribute.type.id, attribute.id, output_type,
-            attribute.type.nullable)
-
         input_type = self._NarrowInputType(attribute.type.id)
         if self._nnbd and attribute.type.nullable:
             input_type += '?'
@@ -1536,7 +1540,6 @@ class Dart2JSBackend(HtmlDartGenerator):
             return self._AddConvertingGetter(attr, html_name, conversion)
         return_type = self.SecureOutputType(attr.type.id,
             nullable=attr.type.nullable)
-        native_type = self._NarrowToImplementationType(attr.type.id)
         self._members_emitter.Emit(
             '\n  $RENAME'
             '\n  $METADATA'