Allow error-recovery in top-level nodes.

dart/frog/leg/scanner/node_scanner_bench.dart

Index: dart/frog/leg/scanner/node_scanner_bench.dart
diff --git a/dart/frog/leg/scanner/node_scanner_bench.dart b/dart/frog/leg/scanner/node_scanner_bench.dart
index 3d8d9a9c86179c84fda46a366c63f815e790621d..30d94a8563b850431aa1a659e807cf535b08f6fc 100644
--- a/dart/frog/leg/scanner/node_scanner_bench.dart
+++ b/dart/frog/leg/scanner/node_scanner_bench.dart
@@ -12,7 +12,8 @@
 
 class NodeScannerBench extends ScannerBench {
   int getBytes(String filename, void callback(bytes)) {
-    List s = fs.readFileSync(filename, null);
+    // This actually returns a buffer, not a String.
+    var s = fs.readFileSync(filename, null);
     callback(s);
     return s.length;
   }