improve fasta export directive recovery

pkg/compiler/lib/src/parser/element_listener.dart

Index: pkg/compiler/lib/src/parser/element_listener.dart
diff --git a/pkg/compiler/lib/src/parser/element_listener.dart b/pkg/compiler/lib/src/parser/element_listener.dart
index 964d1dba7fb912c45d0e0e3afe7bdc8ad945fa67..3f3817a73338aff60b608203fa2604003e6f1eb7 100644
--- a/pkg/compiler/lib/src/parser/element_listener.dart
+++ b/pkg/compiler/lib/src/parser/element_listener.dart
@@ -544,6 +544,8 @@ class ElementListener extends Listener {
     switch (message.code.dart2jsCode) {
       case "MISSING_TOKEN_BEFORE_THIS":
         String expected = arguments["string"];
+        // TODO(danrubel) This functionality is being replaced by

[ahe, 2017/08/22 12:27:00]

Add colon after "(danrubel)".

[danrubel, 2017/08/25 15:30:18]

Fixed in https://codereview.chromium.org/3003263002/

+        // the parser's ensureSemicolon method.
         if (identical(";", expected)) {
           // When a semicolon is missing, it often leads to an error on the
           // following line. So we try to find the token preceding the semicolon