Adding supported checks for XsltProcessor.

sdk/lib/html/dartium/html_dartium.dart

Index: sdk/lib/html/dartium/html_dartium.dart
diff --git a/sdk/lib/html/dartium/html_dartium.dart b/sdk/lib/html/dartium/html_dartium.dart
index f44afd146552ce267ea00d3b632645a75c37de58..61ab8645ef71e3f62bef2520422ef8fe43d54037 100644
--- a/sdk/lib/html/dartium/html_dartium.dart
+++ b/sdk/lib/html/dartium/html_dartium.dart
@@ -29340,6 +29340,9 @@ class XmlSerializer extends NativeFieldWrapperClass1 {
 
 @DocsEditable
 @DomName('XSLTProcessor')
+@SupportedBrowser(SupportedBrowser.CHROME)
+@SupportedBrowser(SupportedBrowser.FIREFOX)
+@SupportedBrowser(SupportedBrowser.SAFARI)
 class XsltProcessor extends NativeFieldWrapperClass1 {
   XsltProcessor.internal();
 
@@ -29347,6 +29350,9 @@ class XsltProcessor extends NativeFieldWrapperClass1 {
   factory XsltProcessor() => XsltProcessor._create();
   static XsltProcessor _create() native "XSLTProcessor_constructor_Callback";
 
+  /// Checks if this type is supported on the current platform.
+  static bool get supported => true;
+
   @DomName('XSLTProcessor.clearParameters')
   @DocsEditable
   void clearParameters() native "XSLTProcessor_clearParameters_Callback";