Ignore mirrors without valid names.

tools/dom/src/html_native_DOMImplementation.dart

Index: tools/dom/src/html_native_DOMImplementation.dart
diff --git a/tools/dom/src/html_native_DOMImplementation.dart b/tools/dom/src/html_native_DOMImplementation.dart
index 701379796bc994b3b7bf9e96832d57e66e0dbaec..457db86b4bc8f5859c873f54ec3062447ff2a45a 100644
--- a/tools/dom/src/html_native_DOMImplementation.dart
+++ b/tools/dom/src/html_native_DOMImplementation.dart
@@ -598,6 +598,7 @@ class _Utils {
     var libraryMirror = classMirror.owner;
     classMirror.declarations.forEach((symbol, declaration) {
       var name = _getShortSymbolName(symbol, declaration);
+      if (name.isEmpty) return;
       if (declaration is VariableMirror) {
         if (accessorPropertiesOnly) return;
         if (!declaration.isStatic) return;
@@ -675,6 +676,7 @@ class _Utils {
     declarations.forEach((Symbol symbol, Mirror declaration) {
       if (declaration is TypedefMirror || declaration is ClassMirror) return;
       var name = _getShortSymbolName(symbol, declaration);
+      if (name.isEmpty) return;
       bool isField = declaration is VariableMirror ||
           (declaration is MethodMirror &&
               treatPropertyAsField(declaration, libraryMirror));