Improve handling of built-in identifiers.

dart/lib/compiler/implementation/scanner/token.dart

Index: dart/lib/compiler/implementation/scanner/token.dart
diff --git a/dart/lib/compiler/implementation/scanner/token.dart b/dart/lib/compiler/implementation/scanner/token.dart
index 86ef6d8cc4c934000910398f15f32eab037ecebf..6821a14f2e6c338e8bea8be201fac6fb148128cf 100644
--- a/dart/lib/compiler/implementation/scanner/token.dart
+++ b/dart/lib/compiler/implementation/scanner/token.dart
@@ -124,11 +124,7 @@ class Token {
    */
   int get precedence => info.precedence;
 
-  bool isIdentifier() {
-    if (kind === IDENTIFIER_TOKEN) return true;
-    if (kind === KEYWORD_TOKEN) return value.isPseudo;
-    return false;
-  }
+  bool isIdentifier() => kind === IDENTIFIER_TOKEN;
 
   /**
    * Returns a textual representation of this token to be used for debugging
@@ -159,6 +155,8 @@ class KeywordToken extends Token {
   KeywordToken(Keyword value, int charOffset)
     : this.value = value, super(value.info, charOffset);
 
+  bool isIdentifier() => value.isPseudo || value.isBuiltIn;
+
   String toString() => value.syntax;
 }