Add back invalid natives that couldn't be removed due to analyzer warnings.

sdk/lib/html/dart2js/html_dart2js.dart

Index: sdk/lib/html/dart2js/html_dart2js.dart
diff --git a/sdk/lib/html/dart2js/html_dart2js.dart b/sdk/lib/html/dart2js/html_dart2js.dart
index 95dda4a8a3c40bb7f8e0effb35991c115bc18c0a..25bc27a488919f9a4013b267fcbd201bfd6465a7 100644
--- a/sdk/lib/html/dart2js/html_dart2js.dart
+++ b/sdk/lib/html/dart2js/html_dart2js.dart
@@ -30880,6 +30880,10 @@ class _SpeechInputResultList extends Interceptor with ListMixin<SpeechInputResul
   // To suppress missing implicit constructor warnings.
   factory _SpeechInputResultList._() { throw new UnsupportedError("Not supported"); }
 
+  @DomName('SpeechInputResultList.length')
+  @DocsEditable()
+  int get length => JS("int", "#.length", this);
+
   SpeechInputResult operator[](int index) {
     if (JS("bool", "# >>> 0 !== # || # >= #", index,
         index, index, length))