Rename $builtinType to $ti

pkg/compiler/lib/src/js_backend/namer.dart

Index: pkg/compiler/lib/src/js_backend/namer.dart
diff --git a/pkg/compiler/lib/src/js_backend/namer.dart b/pkg/compiler/lib/src/js_backend/namer.dart
index 303f52c507e8a3ae5700ba57c116070f9386936e..0d43e7b05b6291cf873de576faf28f83dd31a5bd 100644
--- a/pkg/compiler/lib/src/js_backend/namer.dart
+++ b/pkg/compiler/lib/src/js_backend/namer.dart
@@ -392,6 +392,9 @@ class Namer {
   jsAst.Name get staticsPropertyName =>
       _staticsPropertyName ??= new StringBackedName('static');
 
+  jsAst.Name _rtiFieldName;
+  jsAst.Name get rtiFieldName => _rtiFieldName ??= new StringBackedName(r'$ti');
+
   // Name of property in a class description for the native dispatch metadata.
   final String nativeSpecProperty = '%';