Scan generic method comments with Fasta.

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

Index: pkg/front_end/lib/src/fasta/scanner/token.dart
diff --git a/pkg/front_end/lib/src/fasta/scanner/token.dart b/pkg/front_end/lib/src/fasta/scanner/token.dart
index d72cf9b9daab1e179de45f5890f2390d070fafbd..83a98013e5b66f58f4d088e9393235800f18e022 100644
--- a/pkg/front_end/lib/src/fasta/scanner/token.dart
+++ b/pkg/front_end/lib/src/fasta/scanner/token.dart
@@ -474,6 +474,12 @@ class CommentToken extends StringToken implements analyzer.CommentToken {
             canonicalize: canonicalize);
 
   /**
+   * Creates a non-lazy comment token.
+   */
+  CommentToken.fromString(PrecedenceInfo info, String lexeme, int charOffset)
+      : super.fromString(info, lexeme, charOffset);
+
+  /**
    * Creates a lazy string token. If [asciiOnly] is false, the byte array
    * is passed through a UTF-8 decoder.
    */