Support for new catch syntax in dart2js

dart/tests/language/try_catch_on_syntax_test.dart

+// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+class MyException { }
+
+class MyException1 extends MyException { }
+
+class MyException2 extends MyException { }
+
+class TryCatchTest {
+  static void test1() {
+    var foo = 0;
+    try {
+      throw new MyException1();
+    } 
+    on MyException3 catch (e) { } /// 01: compile-time error
+    on on MyException2 catch (e) { } /// 02: compile-time error
+    catch MyException2 catch (e) { } /// 03: compile-time error
+    catch catch catch (e) { } /// 04: compile-time error
+    on (e) { } /// 05: compile-time error
+    catch MyException2 catch (e) { } /// 06: compile-time error
+    on MyException2 catch (e) {
+      foo = 1;
+    } on MyException1 catch (e) {
+      foo = 2;
+    } on MyException catch (e) {
+      foo = 3;
+    }
+    Expect.equals(2, foo);
+  }
+
+  static void testMain() {
+    test1();
+  }
+}
+
+main() {
+  TryCatchTest.testMain();
+}