Port parser and scanner fixes from rasta branch.

tests/compiler/dart2js/message_kind_helper.dart

Index: tests/compiler/dart2js/message_kind_helper.dart
diff --git a/tests/compiler/dart2js/message_kind_helper.dart b/tests/compiler/dart2js/message_kind_helper.dart
index 03252d1b9deba70f3b3e6c9137e82d318374f965..8e348ac832cf7b15c6dbcde8ea25515cf54848fd 100644
--- a/tests/compiler/dart2js/message_kind_helper.dart
+++ b/tests/compiler/dart2js/message_kind_helper.dart
@@ -22,7 +22,6 @@ const String ESCAPE_REGEXP = r'[[\]{}()*+?.\\^$|]';
 /// However, consider that a single concise diagnostic is easier to understand,
 /// so try to change error reporting logic before adding an exception.
 final Set<MessageKind> kindsWithExtraMessages = new Set<MessageKind>.from([
-  // If you add something here, please file a *new* bug report.

[ahe, 2017/01/28 00:33:33]

Given that we're moving away from this front-end, I think we don't need to worry
about this anymore.

[Johnni Winther, 2017/01/30 09:04:39]

Acknowledged.

   // See http://dartbug.com/18361:
   MessageKind.CANNOT_EXTEND_MALFORMED,
   MessageKind.CANNOT_IMPLEMENT_MALFORMED,
@@ -42,6 +41,7 @@ final Set<MessageKind> kindsWithExtraMessages = new Set<MessageKind>.from([
   MessageKind.UNIMPLEMENTED_METHOD,
   MessageKind.UNIMPLEMENTED_METHOD_ONE,
   MessageKind.VAR_FUNCTION_TYPE_PARAMETER,
+  MessageKind.UNMATCHED_TOKEN,

[ahe, 2017/01/28 00:33:33]

The message is repeated: first during diet parsing, then when parsing the body
again.

I have fixed this problem before (in rasta), but I don't think it matters now.

 ]);
 
 /// Most messages can be tested without causing a fatal error. Add an exception