flag to enable fasta scanner in analyzer

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

Index: pkg/front_end/lib/src/scanner/scanner.dart
diff --git a/pkg/front_end/lib/src/scanner/scanner.dart b/pkg/front_end/lib/src/scanner/scanner.dart
index be259fcf72b9fa6f1795f7fe2f9b078a6f6d7e22..9afaf7da7c1bae97d42dac421fdd370b98460bb6 100644
--- a/pkg/front_end/lib/src/scanner/scanner.dart
+++ b/pkg/front_end/lib/src/scanner/scanner.dart
@@ -202,7 +202,7 @@ abstract class Scanner {
    * Initialize a newly created scanner to scan characters from the given
    * character [_reader].
    */
-  Scanner(this._reader) {
+  Scanner.create(this._reader) {
     _tokens = new Token(TokenType.EOF, -1);
     _tokens.setNext(_tokens);
     _tail = _tokens;