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

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

Index: tools/dom/templates/html/dartium/web_sql_dartium.darttemplate
diff --git a/tools/dom/templates/html/dartium/web_sql_dartium.darttemplate b/tools/dom/templates/html/dartium/web_sql_dartium.darttemplate
index 7c2ffbd93d7b902d05cddc629182946d6c17d8ae..2a5d04abd99c6975b0e27bd4d42c0f30c5107fd7 100644
--- a/tools/dom/templates/html/dartium/web_sql_dartium.darttemplate
+++ b/tools/dom/templates/html/dartium/web_sql_dartium.darttemplate
@@ -24,11 +24,6 @@ import 'dart:nativewrappers';
 import 'dart:_blink' as _blink;
 import 'dart:js' as js;
 
-// 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 web_sqlBlinkMap = {