Hide linter warning for auto-binding-dart.

pkg/polymer/test/build/linter_test.dart

Index: pkg/polymer/test/build/linter_test.dart
diff --git a/pkg/polymer/test/build/linter_test.dart b/pkg/polymer/test/build/linter_test.dart
index ef05428037835abb486799ba1eb191b6331be2f5..3bff05c36b7df6a0ae1d8144272397947fc2f264 100644
--- a/pkg/polymer/test/build/linter_test.dart
+++ b/pkg/polymer/test/build/linter_test.dart
@@ -515,6 +515,10 @@ void main() {
         'warning: definition for Polymer element with tag name "x-foo" not '
         'found. (lib/test.html 0 0)'
       ]);
+    
+    _testLinter('tag exists (internally defined in code)', {
+      'a|lib/test.html': '<div is="auto-binding-dart"></div>',
+      }, []);
 
     _testLinter('used correctly (no base tag)', {
         'a|lib/test.html': '''