fasta tokens implement analyzer token API

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 9afaf7da7c1bae97d42dac421fdd370b98460bb6..48021b7a5756b8b4e1e17f16808d2690b8250694 100644
--- a/pkg/front_end/lib/src/scanner/scanner.dart
+++ b/pkg/front_end/lib/src/scanner/scanner.dart
@@ -126,6 +126,12 @@ class KeywordState {
  */
 abstract class Scanner {
   /**
+   * A flag indicating whether the [Scanner] factory method
+   * will return a fasta based scanner or an analyzer based scanner.
+   */
+  static bool useFasta = false;
+
+  /**
    * The reader used to access the characters in the source.
    */
   final CharacterReader _reader;