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

sdk/lib/svg/dartium/svg_dartium.dart

 library dart.dom.svg;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:_internal' hide deprecated;
 import 'dart:html';
 import 'dart:html_common';
 import 'dart:nativewrappers';
 import 'dart:_blink' as _blink;
 // DO NOT EDIT
@@ skipping 7744 matching lines @@
 // WARNING: Do not edit - generated code.
 
 
 @DocsEditable()
 @DomName('SVGElementInstanceList')
 @Unstable()
 class _ElementInstanceList extends NativeFieldWrapperClass2 with ListMixin<ElementInstance>, ImmutableListMixin<ElementInstance> implements List<ElementInstance> {
   // To suppress missing implicit constructor warnings.
   factory _ElementInstanceList._() { throw new UnsupportedError("Not supported"); }
 
+  @DomName('SVGElementInstanceList.length')
+  @DocsEditable()
+  int get length => _blink.Native_SVGElementInstanceList_length_Getter(this);
+
   ElementInstance operator[](int index) {
     if (index < 0 || index >= length)
       throw new RangeError.range(index, 0, length);
     return _blink.Native_SVGElementInstanceList_NativeIndexed_Getter(this, index);
   }
 
   ElementInstance _nativeIndexedGetter(int index) => _blink.Native_SVGElementInstanceList_NativeIndexed_Getter(this, index);
 
   void operator[]=(int index, ElementInstance value) {
     throw new UnsupportedError("Cannot assign element of immutable List.");
@@ skipping 463 matching lines @@
   @DocsEditable()
   factory _SVGVKernElement() => _SvgElementFactoryProvider.createSvgElement_tag("vkern");
   /**
    * Constructor instantiated by the DOM when a custom element has been created.
    *
    * This can only be called by subclasses from their created constructor.
    */
   _SVGVKernElement.created() : super.created();
 
 }