Use fields in hidden native DOM classes instead of getters/setters.

client/dom/generated/src/frog/SVGFEMergeElement.dart

Index: client/dom/generated/src/frog/SVGFEMergeElement.dart
diff --git a/client/dom/generated/src/frog/SVGFEMergeElement.dart b/client/dom/generated/src/frog/SVGFEMergeElement.dart
index 2c51cd1058449416c1e307eabc365b76839df602..1a6083f4f3a49fb223a6ba29bbfc95a46d45c6da 100644
--- a/client/dom/generated/src/frog/SVGFEMergeElement.dart
+++ b/client/dom/generated/src/frog/SVGFEMergeElement.dart
@@ -3,21 +3,21 @@ class _SVGFEMergeElementJs extends _SVGElementJs implements SVGFEMergeElement na
 
   // From SVGFilterPrimitiveStandardAttributes
 
-  _SVGAnimatedLengthJs get height() native "return this.height;";
+  final _SVGAnimatedLengthJs height;
 
-  _SVGAnimatedStringJs get result() native "return this.result;";
+  final _SVGAnimatedStringJs result;
 
-  _SVGAnimatedLengthJs get width() native "return this.width;";
+  final _SVGAnimatedLengthJs width;
 
-  _SVGAnimatedLengthJs get x() native "return this.x;";
+  final _SVGAnimatedLengthJs x;
 
-  _SVGAnimatedLengthJs get y() native "return this.y;";
+  final _SVGAnimatedLengthJs y;
 
   // From SVGStylable
 
-  _SVGAnimatedStringJs get className() native "return this.className;";
+  final _SVGAnimatedStringJs className;
 
-  _CSSStyleDeclarationJs get style() native "return this.style;";
+  final _CSSStyleDeclarationJs style;
 
   _CSSValueJs getPresentationAttribute(String name) native;
 }