Allow built-in identifiers for labels.

dart/lib/compiler/implementation/scanner/parser.dart

Index: dart/lib/compiler/implementation/scanner/parser.dart
diff --git a/dart/lib/compiler/implementation/scanner/parser.dart b/dart/lib/compiler/implementation/scanner/parser.dart
index a7899f9cdf61c020b04a3ab7d7c4b4e4fc871b1b..f43bddc1f2c4955d7476e928f87da1d11bc1d80e 100644
--- a/dart/lib/compiler/implementation/scanner/parser.dart
+++ b/dart/lib/compiler/implementation/scanner/parser.dart
@@ -774,6 +774,8 @@ class Parser {
       return parseContinueStatement(token);
     } else if (value === ';') {
       return parseEmptyStatement(token);
+    } else if (isIdentifier(token)) {
+      return parseExpressionStatementOrDeclaration(token);
     } else {
       return parseExpressionStatement(token);
     }