Use new try-catch syntax in runtime/, tools/, and utils/.

utils/tests/string_encoding/dunit.dart

Index: utils/tests/string_encoding/dunit.dart
diff --git a/utils/tests/string_encoding/dunit.dart b/utils/tests/string_encoding/dunit.dart
index 11e0860deb8dd36dad74f9c2926cebf16e4d66ac..02586efed67b54afb48bebc4f328cc5ee6fdd672 100644
--- a/utils/tests/string_encoding/dunit.dart
+++ b/utils/tests/string_encoding/dunit.dart
@@ -103,10 +103,10 @@ class TestClass {
         test();
         tearDown();
         return new PassedTest(description);
-      } catch (ExpectException x) {
+      } on ExpectException catch (x) {
         tearDown();
         return new FailedTest(description, x);
-      } catch (var x, var stacktrace) {
+      } catch (x, stacktrace) {
         tearDown();
         return new TestError(description, x, stacktrace);
       }