Switch dart:html objects not to be NativeFieldWrapper subclasses with JsInterop

tools/dom/templates/html/dartium/svg_dartium.darttemplate

 // DO NOT EDIT
 // Auto-generated dart:svg library.
 
 /**
  * Scalable Vector Graphics:
  * Two-dimensional vector graphics with support for events and animation.
  *
  * For details about the features and syntax of SVG, a W3C standard,
  * refer to the
  * [Scalable Vector Graphics Specification](http://www.w3.org/TR/SVG/).
  */
 library dart.dom.svg;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:_internal';
 import 'dart:html';
 import 'dart:html_common';
 import 'dart:nativewrappers';
 import 'dart:_blink' as _blink;
 import 'dart:js' as js;
 
 part '$AUXILIARY_DIR/shared_SVGFactoryProviders.dart';
 
-// Need a default constructor for constructing classes with mixins that are
-// also extending NativeFieldWrapperClass2.  Defining JsoNativeFieldWrapper
-// extending NativeFieldWrapperClass2 creates a default constructor.
-class JsoNativeFieldWrapper extends NativeFieldWrapperClass2 {}
-
 $!GENERATED_DART_FILES
 // FIXME: Can we make this private?
 final svgBlinkMap = {
 $!TYPE_MAP
 };
 
 $if JSINTEROP
 // FIXME: Can we make this private?
 final svgBlinkFunctionMap = {
 $!TYPE_FUNCTION_MAP
 };
 $endif