cleanup duplicate fasta scanner methods

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

Index: pkg/front_end/lib/src/fasta/scanner/abstract_scanner.dart
diff --git a/pkg/front_end/lib/src/fasta/scanner/abstract_scanner.dart b/pkg/front_end/lib/src/fasta/scanner/abstract_scanner.dart
index 7156fae19f05097c57d6b586cc9658e55123092b..ccd5f33389a7d3105275020d33c95db630967c51 100644
--- a/pkg/front_end/lib/src/fasta/scanner/abstract_scanner.dart
+++ b/pkg/front_end/lib/src/fasta/scanner/abstract_scanner.dart
@@ -134,12 +134,12 @@ abstract class AbstractScanner implements Scanner {
   /**
    * Returns the first token scanned by this [Scanner].
    */
-  Token firstToken();
+  Token firstToken() => tokens.next;
 
   /**
    * Returns the last token scanned by this [Scanner].
    */
-  Token previousToken();
+  Token previousToken() => tail;

[ahe, 2017/03/14 14:09:27]

I think we can delete this method.

[danrubel, 2017/03/14 16:55:15]

Done.

 
   /**
    * Notifies that a new token starts at current offset.