Make catch variables final.

pkg/front_end/test/fasta/accessors.dart.direct.expect

Index: pkg/front_end/test/fasta/accessors.dart.direct.expect
diff --git a/pkg/front_end/test/fasta/accessors.dart.direct.expect b/pkg/front_end/test/fasta/accessors.dart.direct.expect
index 04b2ad4952f27627862cd32e32d774c050c7dd32..f76bcfa35e85fe4a34d118b063b31fcf17aec852 100644
--- a/pkg/front_end/test/fasta/accessors.dart.direct.expect
+++ b/pkg/front_end/test/fasta/accessors.dart.direct.expect
@@ -14,7 +14,7 @@ class C extends core::Object {
       core::print(this.onlySetter);
       throw "No error thrown";
     }
-    on core::NoSuchMethodError catch(dynamic e) {
+    on core::NoSuchMethodError catch(final dynamic e) {
       core::print("Expected error: ${e}");
     }
     this.onlySetter = "hest";
@@ -42,7 +42,7 @@ static method main() → dynamic {
     core::print(throw new core::NoSuchMethodError::•(null, #onlySetter, <dynamic>[], <dynamic, dynamic>{}, null));
     throw "No error thrown";
   }
-  on core::NoSuchMethodError catch(dynamic e) {
+  on core::NoSuchMethodError catch(final dynamic e) {
     core::print("Expected error: ${e}");
   }
   self::onlySetter = "fisk";