LibraryMirror interface updated to match dart:mirrors.

utils/apidoc/html_diff.dart

Index: utils/apidoc/html_diff.dart
diff --git a/utils/apidoc/html_diff.dart b/utils/apidoc/html_diff.dart
index 3bf7e4cf2d5074a31754cc5447433c4002919705..31213242f4fdf88ab8d2d8d885a8ae6909007fee 100644
--- a/utils/apidoc/html_diff.dart
+++ b/utils/apidoc/html_diff.dart
@@ -101,7 +101,7 @@ class HtmlDiff {
       warn('Could not find $HTML_LIBRARY_NAME');
       return;
     }
-    for (ClassMirror htmlType in htmlLib.types.values) {
+    for (ClassMirror htmlType in htmlLib.classes.values) {
       final domTypes = htmlToDomTypes(htmlType);
       if (domTypes.isEmpty) continue;