Change a few more uses of the old try-catch syntax.

tests/language/named_parameters4_test.dart

Index: tests/language/named_parameters4_test.dart
diff --git a/tests/language/named_parameters4_test.dart b/tests/language/named_parameters4_test.dart
index ad47cf3560f052c1120a6bd1556880e485bc5a41..035fdf2bec53652d4a83f49a5b3f328dca48e824 100644
--- a/tests/language/named_parameters4_test.dart
+++ b/tests/language/named_parameters4_test.dart
@@ -7,7 +7,7 @@
 // This test is very similar to NamedParameters3Test, but exersizes a
 // different corner case in the frog compiler. frog wasn't detecting unused
 // named arguments when no other arguments were expected. So, this test
-// purposely passes the exact number of positional parameters 
+// purposely passes the exact number of positional parameters.
 
 int test(int a) {
   return a;
@@ -17,7 +17,7 @@ main() {
   bool foundError = false;
   try {
     test(10, x:99);  // 1 positional arg, as expected. Param x does not exist.
-  } catch (Exception e) {
+  } on Exception catch (e) {
     foundError = true;
   }
   Expect.equals(true, foundError);