Update almost all tests (except co19) to use the new try-catch syntax.

tests/standalone/io/directory_invalid_arguments_test.dart

Index: tests/standalone/io/directory_invalid_arguments_test.dart
diff --git a/tests/standalone/io/directory_invalid_arguments_test.dart b/tests/standalone/io/directory_invalid_arguments_test.dart
index 9d01f2f1c4c0a8ddf2f41e93d9ee098bbfeeb0ce..e7754d86429aca8e6c29213d6b170f0368cb7594 100644
--- a/tests/standalone/io/directory_invalid_arguments_test.dart
+++ b/tests/standalone/io/directory_invalid_arguments_test.dart
@@ -23,19 +23,19 @@ class DirectoryInvalidArgumentsTest {
     try {
       d.existsSync();
       Expect.fail("No exception thrown");
-    } catch (var e) {
+    } catch (e) {
       Expect.isTrue(e is IllegalArgumentException);
     }
     try {
       d.deleteSync();
       Expect.fail("No exception thrown");
-    } catch (var e) {
+    } catch (e) {
       Expect.isTrue(e is IllegalArgumentException);
     }
     try {
       d.createSync();
       Expect.fail("No exception thrown");
-    } catch (var e) {
+    } catch (e) {
       Expect.isTrue(e is IllegalArgumentException);
     }
     testFailingList(d, false);