Complain about built-in identifiers.

pkg/front_end/lib/src/fasta/scanner/token.dart

Index: pkg/front_end/lib/src/fasta/scanner/token.dart
diff --git a/pkg/front_end/lib/src/fasta/scanner/token.dart b/pkg/front_end/lib/src/fasta/scanner/token.dart
index 6cacd012d2b5b5260dfdc555b6dcdb902a9094c9..4a36008167df3d7cf17c563fad797d2aa9cc9939 100644
--- a/pkg/front_end/lib/src/fasta/scanner/token.dart
+++ b/pkg/front_end/lib/src/fasta/scanner/token.dart
@@ -123,6 +123,8 @@ abstract class Token {
   int get charEnd => charOffset + charCount;
 
   bool get isEof => false;
+
+  bool get isBuiltInIdentifier => false;
 }
 
 /**
@@ -174,6 +176,12 @@ class KeywordToken extends Token {
 
   bool isIdentifier() => keyword.isPseudo || keyword.isBuiltIn;
 
+  bool get isBuiltInIdentifier {
+    // TODO(ahe): Remove special case for "deferred" once dartbug.com/29069 is
+    // fixed.
+    return keyword.isBuiltIn || identical("deferred", lexeme);
+  }
+
   String toString() => "KeywordToken($lexeme)";
 }