Create a special PrecedenceInfo for use during parser recovery.

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

Index: pkg/front_end/lib/src/fasta/scanner/precedence.dart
diff --git a/pkg/front_end/lib/src/fasta/scanner/precedence.dart b/pkg/front_end/lib/src/fasta/scanner/precedence.dart
index a4e2f726f0791e4f27cbf66d7efa52f00055fe78..5ff90eed41d30e572579609cb0de2d284e829fb7 100644
--- a/pkg/front_end/lib/src/fasta/scanner/precedence.dart
+++ b/pkg/front_end/lib/src/fasta/scanner/precedence.dart
@@ -229,6 +229,11 @@ const PrecedenceInfo KEYWORD_INFO =
 
 const PrecedenceInfo EOF_INFO = const PrecedenceInfo('EOF', 0, EOF_TOKEN);
 
+/// Precedence info used by synthetic tokens that are created during parser
+/// recovery (non-analyzer use case).
+const PrecedenceInfo RECOVERY_INFO =
+    const PrecedenceInfo('recovery', 0, RECOVERY_TOKEN);
+
 const PrecedenceInfo IDENTIFIER_INFO =
     const PrecedenceInfo('identifier', 0, IDENTIFIER_TOKEN);